Ablation catheters and related systems and methods

ABSTRACT

An ablation catheter having a deformable tip is disclosed herein. In some implementations, the ablation catheter includes a catheter body and a deformable tip secured to the catheter body. In these and other implementations, the catheter body can include a fluid delivery lumen. In these and other implementations, the deformable tip includes one or more valves that are configured to open in response to deformation of the deformable tip. In these and still other implementations, the ablation catheter is configured to permit liquid communication between an interior of the deformable tip and an exterior of the deformable tip. In some implementations, RF energy is transmitted from the interior of the deformable tip to the exterior of the deformable tip via liquid exiting the deformable tip.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.16/633,133, filed Jan. 22, 2020, and entitled ABLATION CATHETERS ANDRELATED SYSTEMS AND METHODS, which is a National Stage Entry ofInternational Patent Application No. PCT/US2018/043529 filed Jul. 24,2018, and claims priority to U.S. Provisional Patent Application No.62/536,877, filed on Jul. 25, 2017. The entire contents of each of theabove-identified patent applications are incorporated herein byreference.

TECHNICAL FIELD

The present technology is generally related to ablation catheters andrelated systems and methods.

BACKGROUND

Abnormal rhythms, generally referred to as arrhythmia, can occur in theheart. Cardiac arrhythmias develop when abnormal conduction in themyocardial tissue modify the typical heartbeat pattern. Radio frequency(“RF”) catheter ablation can be used to form lesions that interrupt themechanism of abnormal conduction to terminate certain arrhythmias.

DESCRIPTION OF DRAWINGS

The disclosure will be understood more fully from the detaileddescription given below and from the accompanying drawings of variousimplementations of the disclosure. The drawings, however, should not betaken to limit the disclosure to the specific implementations, but arefor explanation and understanding only.

FIG. 1 schematically illustrates an ablation system configured inaccordance with an implementation of the present technology during anablation treatment.

FIG. 2 is a perspective view of an ablation catheter of the ablationsystem shown in FIG. 1 .

FIGS. 3 and 4 are perspective and side cross-sectional views,respectively, of a distal end region of the ablation catheter shown inFIG. 2 .

FIG. 5 is an enlarged view of a conformable tip of the ablation cathetershown in FIG. 2 .

FIG. 6 illustrates a shape activated valve in a closed state (left) andin an open state (right).

FIG. 7 is a simplified cross-sectional view of the conformable tip ofthe catheter shown in FIG. 2 , showing a change in a wall thicknessalong the conformable tip.

FIG. 8 schematically illustrates a method of inserting the ablationcatheter shown in FIG. 2 into a patient.

FIGS. 9 and 10 are examples of screen shots of a monitor of the ablationsystem shown in FIG. 1 during treatment.

FIGS. 11 and 12 are perspective and cross-sectional views, respectively,of an alternative conformable tip, which includes hemispherical recessedregions.

FIGS. 13 and 14 are perspective and cross-sectional views, respectively,of a conformable tip, which includes inwardly flared slits.

FIG. 15 is a cross-sectional view of a conformable tip, which includescross-slits, relieved near their intersection on the external surface.

FIG. 16 is a cross-sectional view of a conformable tip, which includesthree-legged slits.

FIG. 17 is a perspective view of a conformable tip, which includesprojections extending from its outer surface.

FIG. 18 is a perspective view of a conformable tip, which includesU-shaped slits forming valve flaps from which projections extend.

FIGS. 19 and 20 schematically illustrate a conformable tip, whichincludes projections and recessed regions including slits, in anundeformed configuration and in a deformed configuration, respectively.

FIG. 21 is a schematic, cross-sectional illustration of a conformabletip, which includes umbrella valves.

FIG. 22 is a perspective view of a conformable tip, which includes aconical support structure along its proximal end region.

FIGS. 23 and 24 are perspective views of conformable tips that includerib structures extending along their proximal end regions.

FIGS. 25 and 26 are perspective and cross-sectional views, respectively,of a conformable tip, which includes multiple ribs extending along itsinner surface.

FIG. 27 is a perspective view of a conformable tip, which includes analternative type of support structure extending along its proximal endregion.

FIG. 28 is a schematic illustration of support members that can bepositioned along a proximal end region of conformable tip.

FIGS. 29 and 30 schematically illustrate a conformable tip, whichincludes support tethers, in an undeformed configuration and in adeformed configuration, respectively.

FIG. 31 is a cross-sectional view of the distal end region of anablation catheter having a conformable tip with two discrete regionsincluding ablation electrode in the form of a conductive layer appliedto its inner surface.

FIG. 32 is a cross-sectional view of the distal end region of anablation catheter that includes a heating element around an irrigationlumen extending through a shaft of the catheter.

FIG. 33 is a cross-sectional view of the distal end region of anablation catheter that includes an ablation electrode disposed in theinterior region of a conformable tip.

FIG. 34 is a schematic illustration of the distal end region of anablation catheter that includes an ablation electrode positioned alongan irrigation lumen extending through a shaft of the catheter.

FIGS. 35-38 illustrate various shapes of conformable tips for ablationcatheters.

FIG. 39 is a cross-sectional view of a conformable tip, which includesthree-legged slits and raised regions extending between slit groupings.

FIGS. 40 and 41 are perspective and cross-sectional views, respectively,of a conformable tip, which includes channels extending between recessedregions.

FIGS. 42 and 43 are perspective views of a distal tip and supportstructure assembly in a disassembled and assembled configuration,respectively.

DETAILED DESCRIPTION A. Overview

The present disclosure is generally directed to devices, systems, andmethods of delivering ablation energy to an anatomic structure of apatient in any one or more of various different medical procedures inwhich ablation energy is delivered to tissue at a treatment site withina patient. For the sake of clarity of explanation, the devices, systems,and methods of the present disclosure are described in the context ofcardiac ablation procedures. However, unless otherwise specified or madeclear from the context, the devices, systems, and methods of the presenttechnology can be utilized in additional medical procedures including,but not limited to, ablating tumors in cancer treatment andelectro-surgery procedures in which tissue is cut and substantiallysimultaneously cauterized to avoid or minimize bleeding.

Many of the ablation catheters described herein can be used to formlarger lesions than most conventional ablation catheters. The size ofnon-collapsible ablation catheter tips, which are utilized by mostconventional ablation catheters, is limited by the size of the sheaththrough which the ablation catheter is passed to introduce the ablationcatheter into the patient's vasculature. Lesions that can be formed bysuch ablation catheters are, in turn, limited by the approximate surfacearea of the tip that comes into contact with targeted tissue and theamount of energy that can be safely delivered from the relatively smalltip. In contrast with such conventional ablation catheters, the tips ofmany of the ablation catheters described herein are collapsible andexpandable and can thus be delivered in a collapsed state through asheath and then expanded to a larger size after delivery into thepatient. Because these tips are capable of expanding to sizes (e.g.,diameters) larger than the sheaths through which they are delivered andby conforming their shape to tissue to further increase the tip tissuesurface area, a greater surface area of the tip, as compared to tips ofmany conventional ablation catheters, can be placed in contact withtissue of the patient, allowing a greater amount of energy to bedelivered to the tissue. This can enable the formation of lesions havingincreased widths (e.g., diameters) and, in many cases, increased depths.

In certain implementations, the tip is conformable to the tissue beingtreated. This is expected to help ensure that a large surface area ofthe tip contacts the tissue even when the tissue being treated is notflat or smooth. Lesion characteristics are difficult to control usingmany conventional ablation catheters. One reason for this is that manyconventional ablation catheter tips tend to be small and rigid.Depending on the surface topography of the tissue to be treated and therelative orientation between the catheter tip and tissue, it can bedifficult to obtain a consistent amount of surface area interfacing withtissue. In some cases, the topography of the tissue can, for example,cause only a small area of the tip to contact the tissue (e.g., bycausing only an edge region of the tip to contact the tissue.) Theconformability of many of the catheter tips described herein can help toavoid outcomes like this. Thus, these catheter tips tend to providelarger and/or more consistently sized lesions.

In many implementations, the catheter tip includes shape-activatedvalves that allow liquid (e.g., saline) within the catheter tip to flowout of the catheter tip toward tissue in contact with the catheter tipwhile limiting the amount of liquid (e.g., saline) that flows out ofregions of the tip that are not in contact with the tissue. This designcan help to ensure that most of the energy being delivered by theablation catheter is used to ablate the tissue intended to be ablated.In addition, treatments can be carried out more efficiently with such adesign. For example, because most of the energy is being directed to thetissue being treated, many of the catheters described herein can createlesions that are larger than lesions created by most conventionalablation catheters while using the same amount of energy or even lessenergy than those conventional catheters.

The catheter tip, in many implementations, is able to selectivelyirrigate areas that come into contact with tissue, while providingsubstantially less irrigation in areas that do not. This is expected toensure that sufficient irrigation is available in the area engagingtissue in order to avoid overheating and clot formation at thetip-tissue interface. Many existing devices have a uniform irrigationhole pattern. As a result, areas of the tip electrode that come intocontact with tissue impede fluid flow and receive less irrigation, whichcan lead to excessive heating, blood coagulation and steam pop incertain circumstances.

In many cases, shape activated valves are distributed throughout thecatheter tip in a manner to allow liquid to escape the catheter tip inany of multiple different directions around the tip. The liquid can, forexample, be emitted from the distal end of the catheter tip when thedistal end is brought into contact with tissue, and can be emitted froma side region of the catheter tip when the side region is brought intocontact with tissue. Excluding the region occupied by the shaft body,the liquid can be emitted from the proximal end of the tip when theproximal end of the tip adjacent to the shaft body is brought intocontact with tissue. This permits energy to be selectively delivered totissue contacting the catheter tip regardless of the relativeorientation between the catheter tip and tissue. Moreover, in manycases, the energy can be delivered via these different tip regions withabout the same tissue-tip contact geometry such that lesions of aboutthe same size and shape can be formed in tissue adjacent the distal endof catheter tip, adjacent the proximal region of the catheter tip, orsomewhere in between. This versatility of the catheter tip is expectedto allow a single ablation catheter to achieve highly consistent lesionsregardless of the catheter body or tip orientation required to accessthe target region of tissue. Lesion consistency is also expected to beimproved with a conformal tip because much of the tissue surface wherethe lesion is applied is covered with the tip and irrigation flow ispredictable. In contrast, with conventional ablation catheters, lesionsize is affected by blood flow that convectively cools the tissuesurface. Because blood flow varies greatly between different areas ofthe heart, this contact and/or cooling leads to variability in lesionsize. Lesion consistency can also be improved because the conformal tipconforms to tissue surface, providing a larger area for engagement. Assuch, it is likely that relative motion between the tip and tissue willbe reduced. In contrast, with a conventional catheter, the catheter canbecome dislodged altogether and/or move in response to a heartbeatand/or respiration, and catheter movement can cause variability inlesion size.

In some implementations, the surface area of the catheter tip thatcontacts the tissue during treatment is larger than the surface area ofmany conventional ablation catheter tips, and/or the catheter tip issofter than such conventional catheters. This design can allow a greaterforce to be applied to the tissue by the catheter tip without damaging(e.g., perforating) the tissue because the force is distributed over agreater area leading to a more uniform and lower maximum pressure.

The configuration of the sensors in many of the ablation cathetersdescribed herein allows for improved feedback related to certaincharacteristics of the lesion being formed by the ablation catheter. Thetemperature sensors (e.g., thermistors) of many of the ablationcatheters described herein, for example, are thermally insulated fromthe ablation electrode (e.g., conductive ink) that generates the energyto be delivered to the tissue for ablation. In many cases, the ablationelectrode is located along an inner surface of the tip material, and thetemperature sensor is located along an outer surface of the tip materialor is embedded within the tip material. As a result, the thermallyinsulating material of the tip inhibits the temperature sensor fromdetecting heat conduction to or from the inside of the ablationelectrode. In addition, the catheter tip can conform to the tissue inmany implementations, which can help to ensure that the temperaturesensor, or a thermally conductive material to which the temperaturesensor is attached, directly contacts the tissue being ablated. This canfurther help to improve the accuracy with which the temperature sensorcan detect the temperature of the tissue being ablated. As a result ofthis design, many of the ablation catheters described herein can achievemore accurate tissue temperature measurements than conventional ablationcatheters that include a single temperature sensor coupled to a rigid,sometimes actively cooled, ablation tip. In those conventional ablationcatheters, the temperature sensor tends to detect the temperature of theablation tip (as opposed to that of the tissue alone).

Many of the ablation catheters described herein include sensingelectrodes that can provide improved electrograms and lesion progressfeedback as compared to certain conventional ablation catheters. Thesensing electrodes of ablation catheters described herein, for example,can be positioned on the outer surface of an ablation catheter tip thatis conformable to tissue. The conformability of the catheter tip canhelp ensure that the sensing electrodes directly contact the tissuebeing ablated, which is expected to improve the quality of electrogramsand accuracy with which the lesion size can be estimated based onmeasured impedance values between those electrodes and the returnelectrode. In addition, when measuring the impedance between theablation electrode and a return path, the shape activated valves ensurethat most of the current path flows through tissue under treatment.Because impedance decreases as the lesion is formed, the impedance valuecan be used to assess the size of the lesion. Many conventional ablationcatheters utilize a measured impedance between the ablation electrode(e.g., the electrode tip) and the return electrode. Because the ablationelectrodes of most conventional ablation catheters do not conform to thetissue being ablated and/or do not include shape-activated valves, asignificant portion of the RF current path does not flow through tissueunder treatment, rendering the impedance value less directly related tothat of treated tissue.

Many of the ablation catheter systems described herein allow forimproved detection and monitoring of contact between the ablationcatheter tip and the tissue to be ablated. In certain implementations,for example, the ablation catheter tip is conformable to tissue andincludes a radiopaque material. As a result, deformation of the tipresulting from contact with the tissue to be treated can be easilyvisualized and detected under fluoroscopy.

In some implementations, the ablation catheter tip is equipped withsensing electrodes that can be used to monitor the shape and/or internalfluid volume of the catheter tip. This information can be used tomonitor the degree and location of contact between the catheter tip andthe tissue (sometimes referred to as tip to tissue coupling) and canthus be used to assess certain characteristics, such as size and depth,of the resulting lesion. This can provide the physician with greatercontrol over catheter manipulation and the size of the lesion that isformed.

In some implementations, electrodes are also positioned on an innersurface of the catheter tip. These electrodes can advantageously be usedto detect the state of the catheter tip (e.g., a shape of the cathetertip and/or a level of contact between the catheter tip and tissue) andthe state of valves in the distal tip (e.g., whether those valves areopen or closed). In some examples, these inner electrodes can be used incombination with one or more electrodes positioned on an outer surfaceof the catheter tip to detect the state of the catheter tip and thestate of valves in the distal tip.

In certain implementations, the catheter incudes a concentric electrodethat has a central conductive component surrounded by an annularconductive component. Due to this arrangement, the bipolar signalsconstructed with these two electrodes can reduce or minimize noise andfar field effect in collected signals that allow for improvedelectrograms. Such electrodes can, for example, provide bipolarelectrograms that are more consistent across electrode to tissueorientation than those produced with conventional bipolar electrodes.

Furthermore, by driving current between the two concentric electrodesand monitoring values resulting from the driven current (e.g., impedancevalues, voltage values, current values, etc.), this arrangement canallow for improved detection of contact between the catheter tip (e.g.,a region of the catheter tip including the concentric electrode) andtissue.

In some implementations, a pressure sensor can be placed incommunication with fluid at the catheter tip. The pressure sensor can beused to detect tissue contact and/or to provide feedback to a pump toreach a desired level of irrigation.

Certain details are set forth in the following description and in FIGS.1-43 to provide a thorough understandings of various implementations ofthe disclosure. Other details describing well-known structures andsystems often associated with ablation catheters and related systems andmethods, however, are not set forth below to avoid unnecessarilyobscuring the description of various implementations of the disclosure.

Many of the details, dimensions, angles, and other features shown inFIGS. 1-43 are merely illustrative of particular implementations of thedisclosure. Accordingly, other implementations can have other details,dimensions, angles, and features without departing from the spirit orscope of the present disclosure. In addition, those of ordinary skill inthe art will appreciate that further implementations of the disclosurecan be practiced without several of the details described below.

B. Selected Implementations of Ablation Catheters and Related Systemsand Methods

FIG. 1 schematically illustrates an ablation system 100 configured inaccordance with the present technology during a cardiac ablationtreatment being performed on a patient 102. The ablation system 100includes an ablation catheter 104 that is connected via an extensioncable 106 to a catheter interface unit 108. The catheter interface unit108 can be a computing device that has a display 110, as described inmore detail below. A mapping system 112, a recording system 111, anirrigation pump 114, and an ablation generator 116 are connected to thecatheter interface unit 108. The irrigation pump 114 is also removablyand fluidly connected to the ablation catheter 104 via fluid line 115.The ablation generator 116 is also connected via a wire or cable 117 toa return electrode 118 that is attached to the skin of the patient 102.The recording system 111 can be used throughout the ablation treatmentas well as before or after the treatment. The mapping system 112 can beused prior to or during an ablation treatment in order to map thecardiac tissue of the patient 102 and determine which region or regionsof the cardiac tissue require ablation.

During a subsequent ablation treatment, the ablation generator 116controls and provides energy, e.g., RF energy (e.g., electrical energyin the radiofrequency (RF) range (e.g., 350-600 kHz)) to an ablationelectrode 120 (shown in FIGS. 3 and 4 ) applied to the inner surface ofa conformable distal tip 122 of the ablation catheter 104. At the sametime, the irrigation pump 114 pumps saline to the distal tip 122 of theablation catheter 104 where it contacts the ablation electrode 120.Shape activated valves 124 (shown in FIGS. 2, 3, and 5 ) are provided inmultiple different portions of the distal tip 122. Each of the shapeactivated valves 124, as will be discussed in greater detail below, isconfigured to open when the portion of the distal tip 122 in which thatvalve is located is brought into contact with tissue of the patient 102.The saline is released from the distal tip 122 via the open valve(s) 124and serves to cool environment and as a conduit to deliver the energygenerated by the ablation generator 116 to the tissue adjacent the openvalve(s) 124. The energy travels through the blood and tissue of thepatient 102 to the return electrode 118 and in the process ablates theregion(s) of tissue adjacent the open valves 124 of the distal tip 122.

Because the distal tip 122 is designed so that only the valves 124 inthose regions of the distal tip 122 that are deformed (e.g., due tocontact with tissue) are fully opened to permit the saline to passtherethrough, the undesired application of energy to surrounding bloodof the patient will be reduced. By directing the saline to a specifictargeted tissue region to be treated, this tip design can also increasethe efficiency with which the RF ablation treatment can be carried out.For example, less energy can be delivered to the distal tip 122, ascompared to the amount of energy required to be delivered to theablation catheter of many conventional catheters that indiscriminatelyemit energy from the ablation electrode in all directions, to carry outthe RF ablation treatment on the targeted tissue. At the same time, thefully open valves 124 help to ensure that a sufficient volume of salineis delivered to the targeted tissue, which would otherwise be heated themost and is therefore in the greatest need of irrigation. This helps toprevent the targeted tissue from overheating and thus helps to preventthe generation of steam pop and/or blood coagulation. As will bediscussed in greater detail below, by directing or guiding the salinetoward the targeted tissue and limiting the amount of saline directed tonon-targeted tissue regions, the distal tip 122 can also allow for moreaccurate tracking of the progression of the lesion. For example,impedance values that are measured between the ablation electrode in thedistal tip 122 and the return electrode 118 will be more closelycorrelated with the state of the tissue being treated.

Referring to FIG. 2 , a handle 126 of the ablation catheter 104 isattached to a proximal end region of a catheter shaft 128, and thedistal tip 122 is attached to a distal end region of the catheter shaft128. The handle 126 includes a housing 127 and lever mechanism 129. Thelever mechanism 129 can be operated to deflect the distal end region ofthe catheter shaft 128. The proximal end region of the handle 126includes a fluid line connector (e.g., a luer connector) 133 to whichthe fluid line 115 extending from the irrigation pump 114 can beconnected for delivering saline the ablation catheter 104. The proximalend region of the handle 126 also includes an electrical connector 135to which the extension cable 106 extending from the catheter interfaceunit 108 can be connected for delivering electrical energy from theablation generator 116 to the ablation catheter 104 and for allowingelectrical and temperature data to be delivered from the distal tip 122to the ablation generator 116 via the catheter interface unit 108.

The handle 126 can be attached to the proximal end region of thecatheter shaft 128 using any of various attachment techniques, such asadhesive bonds, thermal bonds, and mechanical connections. The shaftincludes a tube that is in fluid communication with the fluid line 115extending from the irrigation pump 114 and serves to carry saline fromthe proximal end of the ablation catheter 104 to the distal tip 122. Theshaft also includes electrical wires that carry signals from varioussensors on the distal tip 122 to the catheter interface unit and thatcarry electrical power from the ablation generator to the distal tip122. The shaft further includes wires that are attached at their distalends to a ring secured to a distal end region of the catheter shaft 128and that are attached at their proximal ends to the lever mechanism 129of the handle 126 to allow the user to apply tension to the wires todeflect the distal end region of the catheter 104 for steering purposes.

In some cases, a magnetic position sensor is also positioned in thedistal end region of the catheter shaft 128. The position sensor can,for example, include one or more coils configured to detect signalsemanating from magnetic field generators. One or more coils fordetermining position with five or six degrees of freedom can be used.The magnetic field detected by the position sensor can be used todetermine the position of the distal end of the catheter shaft 128.

The distal end region of the catheter shaft 128 includes electrodes 134.These can be used for measuring unipolar and bipolar electrograms. Thesame electrodes can also be separately or concurrently used to supportan impedance or current based localization system. A location signal,either passively measured or driven between these electrodes and anothernode, can be used to determine electrode and/or catheter location. Inaddition, the electrodes can be used to relate location signals (e.g.potential field measurement and/or impedance) measured through them,with locations determined using an independent localization system (e.g.a magnetic localization system described above) to support a hybridmagnetic and impedance based localization.

As shown in FIGS. 3 and 4 , the outer surface of the distal end regionof the catheter shaft 128 is attached to the inner surface of a neck 130of the distal tip 122. A metallic electrode 134 is positioned over theneck 130 of the distal tip 122 to apply a compression force between theinner surface of the neck 130 and the outer surface of the cathetershaft 128. The metallic electrode 134 can, for example, be swaged to theneck 130. A projection 137 extends from the inner surface of the neck130 and sits within a recess formed in the catheter shaft 128 to providethe neck 130 and the catheter shaft 128 with a further mechanicalconnection that helps to prevent axial movement of the distal tip 122relative to the catheter shaft 128. Alternatively, or additionally, theinner surface of the neck 130 can include a recess that receives aprojection extending from the outer surface of the catheter shaft 128 toprovide a mechanical connection between those components. Alternatively,or additionally, an appropriate (e.g. RTV silicone) adhesive can be usedto bond the neck and/or the protrusion to the distal end of the shaft.

The catheter shaft 128 can be formed of any of various differentbiocompatible materials that provide the catheter shaft 128 withsufficient pushability and flexibility to allow the catheter shaft 128to be navigated through blood vessels of a patient. Examples of suitablematerials from which the catheter shaft 128 can be formed includepolyether block amide sold under the trademark PEBAX and commerciallyavailable from Arkema, Inc. of King of Prussia, nylon, polyurethane,thermoplastic polyurethanes sold under the trademark PELLETHANE, andcommercially available from Lubrizol Corp. of Wickliffe, OH, and/orsilicone. In certain implementations, the catheter shaft 128 includesmultiple different materials along its length. The materials can, forexample, be selected to provide the catheter shaft 128 with increasedflexibility at the distal end, when compared to the proximal end of thecatheter shaft 128, which can help to provide the catheter shaft 128with sufficient levels of pushability and flexibility to allow thecatheter shaft 128 to traverse tortuous blood vessels, while stillallowing flexing and steering of the distal end. The catheter shaft 128can also include a tubular braided element that provides torsionalstiffness while maintaining bending flexibility to one or more regionsof the catheter shaft 128.

The ablation catheter 104 is typically provided with a sheath (e.g., aninsertion sheath) 139 (shown in FIG. 8 ) that can be positioned aroundthe distal end region of the catheter shaft 128 and the distal tip 122to constrain the distal tip 122 in a collapsed position. Constrainingthe distal tip 122 in a collapsed configuration in this way permits thedistal tip 122 to be inserted into a patient via an introducer sheathprior to carrying out an ablation treatment. After being used toposition the collapsed distal tip 122 within the introducer sheath, theinsertion sheath 139 can be proximally retracted from the distal tip122.

Referring now to FIGS. 3-5 , which show the distal tip 122 in a nominalor expanded state, the distal tip 122 includes a generally sphericalbody 132 that extends distally from the neck 130. The spherical body 132is capable of conforming to tissue. In addition, the spherical body 132is collapsible to a size (e.g., diameter) significantly smaller than thesize (e.g., diameter) of the spherical body 132 in its nominal orexpanded state. As will be discussed below, the collapsibility of thespherical body 132 allows the distal tip 122 to be delivered via asheath (e.g., an 8F introducer sheath) and through the vasculature ofthe patient to a treatment site and then allowed to elastically expandto a significantly larger diameter, which allows for the formation oflarger lesions than many conventional ablation catheters that do notinclude collapsible and expandable ablation tips.

The spherical body 132 can be any size that allows the distal tip 122 tobe delivered to a region of tissue to be treated and that is capable ofgenerating a lesion of a size desired by the operator (e.g., physician).In certain implementations, the spherical body 132 of the distal tip 122has a diameter of 2.0 mm to 25 mm (e.g., 5 mm, 10 mm, and 12 mm). Thewall thickness of the spherical body 132 can have a thickness of 10 μmto 1000 μm (e.g., 25 μm to 800 μm, 25 μm to 400 μm, 50 μm-500 μm, 100μm-1000 μm, and so forth).

The spherical body 132 of the distal tip 122 can be formed of one ormore biocompatible materials that allow the spherical body 132 toconform to tissue and to be collapsed within a sheath while alsoproviding sufficient strength or rigidity to permit shape activation ofthe valves 124. In some implementations, the material from which thespherical body 132 and the neck 130 are formed has a durometer of 10shore A to 70 shore D (e.g., 40 shore A). In certain implementations,the spherical body 132 and the neck 130 include one or more of silicone,fluorosilicone, urethane, polyethylene, a polycarbonate-basedthermoplastic urethane sold under the trademark CHRONOFLEX andcommercially available from AdvanSource Biomaterials of Wilmington, MA,a biocompatible elastomer solder under the trademark CHRONOPRENE, alsocommercially available from AdvanSource Biomaterials, PEBAX, Nylon,polyurethane, etc. In some implementations, the material from which thespherical body 132 is formed can be loaded with a radiopaque additive,such as a barium sulfate additive. The radiopaque additive permits thespherical body 132 to be visualized using fluoroscopy during an ablationtreatment.

In some implementations, the spherical body 132 is formed of a materialthat has a relatively high thermal conductivity and a relatively lowelectrical conductivity. The spherical body 132 can, for example, beformed of a polymer, such as silicone, that is loaded with a material,such as barium sulfate or bismuth. Adding certain materials with highthermal conductivity to the polymer body can increase the thermalconductivity of the body, which can help to distribute heat throughoutthe material of the distal tip 122 and prevent localized hot spots.

In certain implementations, the spherical body 132 has a diameter of 10mm, a wall thickness of 150 μm, and is formed of silicone loaded withbarium sulfate. It has been found that such a construction allows thedistal tip 122 to be retracted through an 8F introducer sheath fordelivery into the patient and enables operation of the shape activatedvalves 124 under normal conditions of use.

As shown in FIG. 5 , the spherical body 132 of the distal tip 122 formsmultiple triangular or tetrahedral depressions 136 that extend inwardlyfrom the outer surface of the distal tip 122. More specifically, thedepressions or recesses 136 are formed by the outer surfaces of threetriangular walls 138 that extend inwardly (i.e., toward the interior ofthe spherical body 132). These walls 138, as shown in FIGS. 3 and 4 ,project inwardly into the interior volume of the spherical body 132 toform projections 140 in the shape of tetrahedrons. Each wall 138 of eachprojection 140 is structurally connected to an adjacent wall 138 of aneighboring projection 140 by a rib 142. The ribs 142 extend between theinner surfaces (i.e., the surfaces exposed in the interior volume of thespherical body 132) of the walls 138 of the various neighboringprojections 140.

Still referring to FIGS. 3 and 4 , a slit 144 is formed in a boundaryregion between each of the triangular walls 138 within each of theprojections 140. Each of the slits 144 extends inwardly from a pointnear the outer surface of the spherical body 132 to the apex of thetetrahedron projection 140 where it connects with the other two slits144 in the projection 140 to form the shape activated valve 124. As aresult of this slit configuration, each of the walls 138 of a givenprojection 140 is permitted to move relative to the two other walls 138of the projection 140. Movement of the walls 138 relative to one anotherallows the slits 144 to increase and decrease in size and thus permitsthe shape activated valves 124 to be opened and closed.

Referring to FIG. 6 , as a normal force is applied to the outer surfaceof the distal tip 122 in the vicinity of one of the shape activatedvalves 124, one or more of the three side walls 138 move away from eachother, thereby increasing the size of the slits 144 and opening thevalve 124. As the region of the distal tip 122 contacted by the tissuedeforms from its normal nominal shape to a deformed, more concave shape,the inner and outer surfaces of the distal tip 122 bend at differentbending radii. Due to the deformation of the wall of the distal tip 122in this way, the inner surface experiences tensile forces, while theouter surface experiences compressive forces. The tension at the innersurface of the distal tip 122 causes the walls 138 of the valves 124experiencing the tensile force to move away from one another. Becausethe side wall regions that form the slits 144 are radially inwardlyspaced from the outer surface of the distal tip 122, those side wallregions tend to experience tensile forces in response to radially inwarddeformations of the distal tip 122. This helps to ensure that the slits144 widen to open the valves 124 as the distal tip 122 is deformed.

The ribs 142 that extend between walls 138 of adjacent valves 124provide the valve walls with increased rigidity for valve function,while also occupying a relatively small volume. This permits the averagewall thickness of the distal tip 122 to be kept very small (e.g., 0.15mm), which provides the distal tip 122 with high flexibility and theability to be collapsed to small sheath diameters (e.g., 2 mm to 3 mm).Thus, the ribs 142 help to ensure that the distal tip 122 is collapsibleto an extent that the catheter 104 can be navigated through bloodvessels of the patient and can then be expanded to its normal, sphericalshape at a treatment site. The thin wall structure of the distal tip122, which is permitted in part by the presence of the ribs 142,provides the distal tip 122 with sufficient flexibility to be deformedby relatively small forces (e.g., 1 to a 100 grams, 20 to 100 grams, 30to 100 grams, 40 to 100 grams, 75 to 100 gram, and so forth) applied tothe distal tip 122 during ablation treatments as a result of contactbetween the distal tip 122 and the tissue being ablated.

Due to the tension experienced at the inner surface of the distal tip122 as the distal tip 122 is radially inwardly deformed, the ribs 142associated with those valves 124 in the regions experiencing the tensionalso tend to pull the side walls 138 to which the ribs 142 are attachedaway from the center regions of the valves 124, thereby widening theslits 144. In this way, the ribs 142 can help to facilitate opening ofthe valves 124. The ribs also help to prevent the valves 124 fromopening in response to internal fluid pressure within the distal tip122.

The tetrahedral recesses 136 formed by the outer surfaces of the sidewalls 138 provide relief to portions of the outer surface of the distaltip 122 that experience compression during radially inward deformationof the distal tip 122. The tetrahedral recesses 136 also act to counterany tendency of the valve to close near the outer surface due to thesecompression, resulting in a reduction the force required to deform thedistal tip 122 and open the valves 124 in the deformed region of thedistal tip 122.

The structure of the distal tip 122 can allow the valves 124 to beopened with very little force applied to the distal tip 122. Asdiscussed below, the ability of the valves 124 to reliably open in thismanner can help to ensure that the valves 124 in the region(s) of thedistal tip 122 that contact(s) tissue during treatment will allow salineto exit those valves 124 and carry energy, e.g., electromagnetic energyand RF energy, to the adjacent tissue to ablate the tissue. Because onlythe valves 124 in deformed regions of the distal tip 122 tend to fullyopen, the design of the distal tip 122 tends to restrict the release ofsaline (and thus the energy carried by the saline) largely to regions ofthe distal tip 122 in proximity to tissue deforming the distal tip 122.The valves 124 that are in undeformed regions of the distal tip 122 tendto remain closed. As a result, the amount of saline and energy deliveredto the surrounding area not in contact with the distal tip 122 islimited and wasted energy, e.g., energy directed away from the tissue,is minimized.

In addition, limiting the amount of saline (and energy carried by thesaline) that is released from those closed valves 124 helps to ensurethat most of the electrical energy delivered to the saline by theablation generator is transmitted to the tissue desired to be ablatedvia the open valves 124 resulting in an efficient treatment. Carryingout the treatment efficiently in this manner (i.e., without significantenergy losses to locations that are not desired to be treated) allowsthe use of relatively low power ablation generators. In many cases, forexample, the same ablation generators that are used to powerconventional ablation catheters having rigid ablation tips of muchsmaller diameters than the expanded distal tip 122 can be used to carryout procedures using the ablation catheter 104.

Limiting the amount of saline delivered into the patient in this wayalso helps to prevent patients from becoming overloaded with fluid andcan prevent additional treatments and complications that are associatedwith excess fluid in patients.

In addition, more efficient delivery of energy to tissue can enablestandard ablation generators to produce larger lesions than thoseproduced by standard ablation catheters, with rigid ablation electrodes.As larger areas of tissue are engaged, more current is required toachieve the requisite current density in the tissue targeted fortreatment. Using the same energy limits, while directing all or most ofthe available current toward the targeted tissue enables a larger areato be ablated relative to the area that would be ablated by mostablation catheters.

To help ensure that the contact region of the distal tip 122 experiencesdeformation upon contacting tissue, the neck 130 and the proximal endregion of the spherical body 132 have a greater wall thickness than thedistal portion of the spherical body 132, as shown in FIG. 7 , whichillustrates a simplified cross-section of the distal tip 122.Specifically, the wall thickness is greatest at the neck 130 andgradually decreases up to about the mid-point (i.e., the equator) of thespherical body 132. The thicker proximal end region and of the distaltip 122 and neck 130 act as a support structure to limit proximalmovement of the proximal end region of the distal tip 122 in response toa proximal force being applied to the distal end portion of the distaltip 122 or in response to a bending moment be applied from a lateralforce in the case of side-contact.

As the ablation catheter 104 is advanced distally into contact withtissue, a proximal axial force will be applied to the distal end of thedistal tip 122. Alternatively, as the tip is flexed into side-contactwith tissue, a lateral force at the contact region will result in abending moment at the neck. The added axial and bending stiffnessprovided by the thickened walls at the proximal end region of the distaltip 122 inhibits (e.g., prevents) deformation of the proximal end regionof the distal tip 122 resulting from these forces and thus permitslocalized deformation at the tissue contact region of the distal tip122. The localized deformation in the tissue contact region of thedistal tip 122 causes the valves 124 within the deformed region to openand thus allows saline carrying energy to escape through those valvesduring treatment to ablate tissue adjacent the deformation. The valves124 in the undeformed regions of the distal tip 122 will remain closed,thereby limiting the escape of saline and energy to tissue and bodilyfluids other than the tissue adjacent the deformed distal end region ofthe distal tip 122.

The distal half of the spherical body 132 in FIG. 7 has an approximatelyconstant wall thickness that is less than the neck 130 and the proximalhalf of the spherical body 132. In other implementations, the wallthickness can increase again in the distal end region of the sphericalbody 132. This can, for example, increase the ease with which the distaltip can be manufactured using certain manufacturing techniques (e.g.injection or blow-molding.)

Without added support in the proximal end region of the distal tip 122,a proximal axial force and/or a lateral force applied to the distal tip122, might cause the spherical body 132 to shift and/or bend withoutcausing a localized deformation at the distal end of the distal tip 122.This could result in none of the valves 124 being opened or could evenresult in certain valves 124 at the proximal end of the distal tip 122being opened while the valves 124 at the distal end of the distal tip122 remain closed. In addition, if the proximal end region bends, areduced surface of the distal tip engages tissue. As a result, thetissue desired to be treated adjacent the distal end region of thedistal tip 122 would not be ablated, and electric current would beineffectually directed through the open proximal valves. The supportprovided by the thickened wall in the proximal end region of the distaltip 122 can prevent this from occurring.

Referring again to FIGS. 3 and 4 , the ablation electrode 120 of theablation catheter 104 is in the form of a continuous conductive layerapplied to the inner surface of the distal tip 122. The ablationelectrode 120 coats the inner surface of the spherical body 132 and theneck 130 of the distal tip. The ablation electrode 120 is flexible andthus permits the distal tip 122 to expand and collapse without affectingthe ability of the ablation electrode 120 to carry energy. The ablationelectrode 120 can include one or more conductive materials, such assilver, carbon, gold, silver-coated glass beads, graphene, etc.

The neck 130 of the distal tip 122, as described above, is connected tothe distal end region of the catheter shaft 128. The ablation electrodeis electrically connected to the ablation generator via an electricalwire that passes through a lumen of the catheter shaft. The distal endof the wire contacts the ablation electrode and is electricallyconnected to the electrical connector 135 in the handle 126 of theablation catheter 104 and can thus carry electrical signal delivered bythe ablation generator 116 to the ablation electrode 120. In some cases,an electrically conductive adhesive can be used to electrically connectand secure the ablation electrode to the electrical wire. Anelectrically conductive adhesive can also be used between the neck 130and the catheter shaft 128 to secure those components together whileenabling energy to freely pass between those components. In other cases,an external compressive force, e.g., a compressive force provided by theelectrode 134, can also secure the ablation electrode to the electricalwire by compressing the ablation electrode 120 on the inner surface ofthe neck 130 against an electrically conductive member, e.g., a wire,exposed along the outer surface of the distal end region of the cathetershaft 128. A component with an insulating outer surface (e.g. a plastictube) can also be situated beneath the inner surface of an electricallyconductive member, e.g., a wire.

During use, as described in greater detail below, the ablation generator116 delivers energy to the ablation electrode 120 via an electricallyconductive member, e.g., a wire. As saline is pumped into the interiorof the distal tip 122 by the irrigation pump 114 and the saline exitsthe open valves 124 of the distal tip 122, the energy is carried fromthe ablation electrode 120 to tissue of the patient adjacent the openvalves 124 by the saline. Because the ablation electrode carries the RFsignal very close to the valves, it minimizes the impedance added bypassing the current through saline. This, in turn, minimizes energy lossand heating of the saline.

As shown in FIGS. 3-5 , the distal tip 122 includes multiple outersensing electrodes 146, multiple inner sensing electrodes 148, andmultiple thermistors. The outer sensing electrodes 146, as will beexplained in greater detail below, can be used to detect electricalsignals emitted from other electrodes of the distal tip and/or to detectelectrical signals emitted from the heart of the patient during use.Referring to FIG. 5 , each of the outer electrodes 146 includes acentral conductive component 150 and an annular conductive component 152that surrounds the central conductive component. The conductivecomponents 150, 152 are attached to flexible printed circuits 154, whichare attached to the body of the distal tip 122. Each of the conductivecomponents 150, 152 is connected to a wire that extends through thecatheter shaft 128 to the catheter interface unit 108 for transferringdata signals from the conductive components 150, 152 to the control unit(e.g., processor) in the catheter interface unit 108.

The conductive components 150, 152 are typically thin pieces ofthermally and electrically conductive materials. Examples of suitablematerials from which the conductive components 150, 152 can be formedinclude copper, gold, nickel, etc. In certain implementations, theconductive components can be coated with a specialized coating, such assputtered or electroplated iridium oxide. This coating can reduce theelectrical impedance of the saline-electrode interface, thereby reducingnoise pickup for cardiac waveforms with micro-volt scale amplitudes.

The central conductive component 150 typically has the same surface areaas the annular conductive component 152. This can permit the conductivecomponents to have identical impedance to the surrounding blood and canlimit noise when used to provide bipolar intracardiac electrograms. Insome implementations, each of the conductive components has a surfacearea of 0.25 mm 2 to 1 mm² (e.g., 0.5 mm²).

The concentric design of the conductive components 150, 152 reduces andin some cases eliminates the effect on the collected signal of theelectrode pair orientation relative to tissue when the electrode ispressed against the tissue. Because the distal tip conforms to a tissuesurface, the concentric electrodes can be pressed flat against a tissuesurface, which further reduces orientation impact on bipolar signalconstructed with the pair. In addition, the far field effect isminimized because the relatively small size and close spacing betweenthe electrodes helps to ensure that they measure signals from theunderlying tissue. The insulating deformable material of the distal tipalso minimizes the far field effect of signal pickup from neighboringtissue. Furthermore, the separation of these electrodes from theablation electrode reduces noise pickup during ablation. In combination,these properties provide localized electrograms that are consistent andeasily interpreted. Conventional bipolar electrode pairs often havemismatched surface area (e.g., where the surface area of the ablationelectrode exceeds the surface area of the other electrodes) leading toadded noise, a bipolar signal whose amplitude and sign are dependent ontip-tissue orientation, larger electrode sizing resulting in morefar-field signal from adjacent tissue, and more noise as ablative energyis delivered to one electrode in the pair.

The thermistors are attached to the inner surfaces of the flexibleprinted circuit 154, opposite the central conductive components 150 ofthe outer electrodes 146. Each of the thermistors can be used to detectthe temperature of its associated outer electrode 146. Any of varioustypes of thermistors and thermocouples can be used. In certainimplementations, the thermistors are discrete negative temperaturecoefficient elements. Because the thermistors are separated from theouter electrodes 146 by only the thin flexible printed circuit material(e.g. polyimide) with relatively high thermal conductance and areseparated from the ablation source by the thicker distal tip material(e.g. silicone) with relatively low thermal conductance, the electricalresistance of the thermistors can be used to accurately estimate thetemperatures of the outer electrodes 146. Since the outer electrodes 146are exposed along the outer surface of the distal tip 122 and can beplaced in direct contact with tissue of the patient during use, theirtemperature can provide an accurate indication of the tissue temperatureduring treatment. Tissue temperature has been found to be a goodindicator of ablation lesion formation. In some implementations,temperature data from the thermistors can be used as a safety control tostop ablation delivery if overheating (e.g. >90° C.) occurs.

As shown in FIGS. 3 and 4 , the inner electrodes 148 are metal pads thatare attached to the inner surfaces of flexible printed circuits 154,which are attached to the body of the distal tip 122. The innerelectrodes 148 can be formed of the same material and can have the samesurface area of the outer electrodes 146 in order to match the impedanceof the outer electrodes 146. The inner electrodes 148 can be used togenerate and/or measure electrical signals. As will be described ingreater detail below, these signals can be used to determine the shapeand/or interior volume of the distal tip 122 during treatment. Inaddition, they can be used to determine the open/closed state of nearbyvalves.

The flexible printed circuits 154 to which the outer electrodes 146, theinner electrodes 148, and the thermistors are attached can be formed onone or more biocompatible substrates, such as polyimide or parylene.Metallization layers can include copper or gold. Outer layer can includematerials such as polyimide, parylene and others. In some examples, theinsulated layer of the distal tip can include a metallization orconductive ink layer that functions as a conductor. In some cases,electrodes can be selectively applied onto one or more layers of thedistal tip.

After forming the spherical body 132 and the neck 130 of the distal tip122, the material of the spherical body 132 can be cut in desiredregions to form the slits 144 of the valves 124. The slits 144 can beformed using any of various suitable cutting techniques, including lasercutting, and mechanical cutting (e.g., using a lance).

The various electrodes 146, 148 and thermistors can then be attached tothe distal tip 122 using a compliant adhesive, such as a RTV silicone.Alternatively or additionally, the various electrodes and thermistorscan be attached to the distal tip via mechanical retaining features(e.g. tabs) added to the perimeter of the flexible circuits that can beinserted into mating hole or slot features molded into the tip.Alternatively or additionally, the electrodes and thermistors can bemolded or overmolded into the distal tip during its manufacture.Alternatively, staples or sutures, e.g., of Nylon, can be used to fastenthe electrodes and thermistors to the tip.

In some implementations, an additional thermistor can be mounted inthermal contact with the ablation electrode or somewhere inside the tipin thermal communication with the saline. Temperature data from thisthermistor can be used as a safety control to stop ablation delivery ifoverheating (e.g. >90° C.) occurs.

In certain implementations, a pressure sensor (e.g., a MEMSpiezo-resistive element) for measuring internal fluid pressure can alsobe provided in the distal tip 122. The internal fluid pressure sensorcan be connected to the catheter interface unit 108 via a wire or cableto transmit pressure data to the control unit of the catheter interfaceunit 108. This pressure data can be used by the control unit to controlthe flow rate of saline delivered to the distal tip 122 by theirrigation pump 114. The pressure data can also be used to indicatewhether the distal tip 122 is in contact with tissue and to indicate thestate of the various valves 124. For example, when the tip is pressedagainst tissue, causing the valves to open, the resulting fluid pressuredrop could be used along with other information to assess the extent ofcontact. This pressure sensor can be used to titrate irrigation and/orinitiate one or more pressure relief functions, e.g., activating one ormore pressure relief valves (not shown). Furthermore, such pressuredrops would not be as apparent if measured with a sensor at the proximalend of the irrigation lumen due to that lumen's high fluid flowresistance (as a long, narrow tube). As such, it is advantageous forthis reason to have a pressure sensor near the tip, on the other side ofthat resistive lumen. In an example with a uniform hole pattern, ratherthan shape activated valves, the pressure sensor will indicate theamount of surface area engaging with tissue. Holes pressed againsttissue will experience greater resistance to flow and subsequently causean increase in pressure. The increase in pressure for a given flow willprovide an indication of amount of coupling between the tip and tissue.

Referring again to FIG. 1 , the catheter interface unit 108 acts as theinterface between the ablation catheter 104 and other instrumentation ofthe ablation system 100. In some implementations, the catheter interfaceunit 108 acts as a control unit for controlling the ablation system 100.The mapping system 112, the recording system 111, the irrigation pump114, and the ablation generator 116 are connected to the catheterinterface unit 108 via electrical cables 155, 156, 157, and 159,respectively.

The catheter interface unit 108 is operably connected to the ablationgenerator 116 such that the catheter interface unit 108 can receive datafrom the various sensors and/or control the output of or communicatewith the ablation generator 116 according to a predetermined schemeand/or user input. The catheter interface unit 108 can be a computingdevice that is running a general purpose operating system (e.g., aUnix-like operating system such as Linux). The catheter interface unit108 can include any suitable logic processor (e.g., control circuit),hardware, software, firmware, or any other logic control adapted toperform the features discussed herein. In some implementations, theablation generator 116 includes its own controller for controlling thegenerator based on data received from the sensors at the distal tip 122.

The catheter interface unit 108 can also include a current source thatcan generate a signal at a frequency above the cardiac band (e.g., 5kHz). The signal can be a sinusoidal signal with an amount of currentbelow the stimulation threshold of cardiac tissue. For example, at 5kHz, 50 μA can be safely used in the cardiac chamber. The signal can begenerated as current driven between various sets of electrodes on thecatheter 104, or between those electrodes and the ablation returnelectrode, and/or between those electrodes and other cutaneouselectrodes while collecting corresponding data in response to thiscurrent on other driven and passive electrodes. In order to drivemultiple sets of electrodes and generate corresponding measurements,various multiplexing schemes such as time division, frequency division,code division and any combination thereof can be used. The currentsource and acquisition hardware can be implemented using discrete analogcircuitry to modulate and demodulate the signals, and can also usedigital to analog and analog to digital conversion to perform some ofthese tasks digitally using elements such as a central processing unit,digital signal processor, field programmable gate array, etc.

As an alternative to or in addition to driving current betweenelectrodes, a sinusoidal or square wave voltage can be driven betweenthem. For example, the catheter interface unit 108 can include a voltagesource that can generate a sinusoidal or square wave voltage signal at aparticular frequency, thereby resulting in a current having a particularmagnitude (e.g., a magnitude below the stimulation threshold of cardiactissue).

The catheter interface unit 108 includes a user interface panel, whichtypically includes the display 110, indicators, and switches to permitthe operator to monitor and control delivery of energy to the catheter104 from the ablation generator 116. The catheter interface unit 108 canalso include a computer interface module such as a touchscreen and/orkeyboard and mouse. The catheter interface unit 108 can display avariety of information related to the ablation procedure. For example,the catheter interface unit 108 can display a digital readout of theactual power, voltage and current being delivered, the calculatedimpedance (e.g., based on measured current and voltage) between theablation electrode 120 and the return electrode 118 during the deliveryof energy, the measured tissue temperature on the various sensors, thenumber of times the ablation generator 116 has been activated, and/orthe total elapsed time during which energy has been delivered to thepatient. In some cases, the catheter interface unit 108 displays datathat represents the shape of the distal tip 122 or the shape and/orprogress of the lesion being generated by the ablation catheter 104.This information can be represented in graph form, as two-dimensionalimages, and in three-dimensional surface representing the distal tip.The information can also be transferred to a mapping system and berepresented in a three-dimensional electro-anatomical context.

The irrigation pump 114 is a pumping mechanism that can be connected toa saline reservoir and operated to cause the saline to flow through thecatheter 104 and exit the distal tip 122. In some cases, the irrigationpump 114 contains the fluid reservoir for storing the saline, while inother cases, the irrigation pump 114 can be connected to a separatesource of saline, such as a saline bag. The irrigation pump 114 can, forexample, be a peristaltic pump.

The mapping system 112 includes a mapping signal processor that can beconnected to the sensing electrodes of the ablation catheter 104 todetect electrical activity of the heart. This electrical activity can beevaluated to analyze an arrhythmia and to determine where to deliver theablation energy as a therapy for the arrhythmia.

As discussed above, the return electrode 118 can be separately connectedto the ablation generator 116 via the cable 117. The return electrode118 is configured for attachment to a patient's skin surface to completethe circuit necessary for the application of energy to the tissue of thepatient. During treatment, RF power that is supplied by the ablationgenerator 116 is transmitted through tissue of the patient, between theablation electrode 120 in the distal tip 122 of the catheter 104 and thereturn electrode 118, to heat the tissue in the immediate vicinity ofthe tip to a temperature sufficient to cause ablation. The heating ofthe tissue can be controlled by the catheter interface unit 108 orablation generator 116, through controlling the amount of energygenerated by the ablation generator 116 and the amount of irrigationdelivered by the pump. The RF power that is supplied can be chosen suchthat the desired amount of tissue ablation occurs.

A method of using the ablation system 100 to perform a cardiac ablationtreatment will now be described. Depending on the specific arrhythmia,the location or region of tissue targeted for ablation can beanatomically guided or determined by mapping the relevant chamber orchambers of interest. Subsequently, those regions of cardiac tissue canbe ablated in the manner described below. In some cases, the ablationcatheter 104 and/or a mapping catheter performs mapping function beforeand/or during an ablation treatment.

To perform a cardiac ablation treatment, the distal end of the ablationcatheter 104 is first introduced into the patient, typically via afemoral vein or artery. FIG. 8 schematically illustrates a series ofsteps carried out to introduce the ablation catheter 104 into thepatient. In step 1, an introducer sheath 160 is positioned within ablood vessel of the patient (e.g., the femoral artery of the patient)and the ablation catheter 104 is positioned for insertion into theintroducer sheath 160. As a second step, the user grasps the handle 126of the catheter 104 and distally advances the insertion sheath 139 alongthe catheter shaft 128 until the insertion sheath 139 surrounds thedistal tip 122. As the insertion sheath 139 is advanced over the distaltip 122, the distal tip 122 collapses to a diameter capable of beinginserted into the introducer sheath 160. The user then, in step 3,inserts the insertion sheath 139 containing the distal tip 122 into theintroducer sheath 160 and distally advances the catheter 104. In step 4,after positioning the distal tip 122 within the introducer sheath 160,the distal tip 122 is advanced out of the insertion sheath that is thenleft surrounding a proximal portion of the catheter shaft 128 throughoutthe remainder of the treatment. As a fifth step, the catheter isadvanced through the introducer sheath 160 and the patient's vasculatureuntil the distal tip 122 reaches the treatment site in the heart of thepatient. As the distal tip 122 is extended distally beyond theintroducer sheath 160, the distal tip 122 of the catheter is allowed toexpand to its nominal configuration.

The advancement of the ablation catheter 104 through the patient's bloodvessels and into the patient's heart is typically viewed underfluoroscopy. While the ablation catheter 104 is being passed through theintroducer sheath and blood vessels of the patient and into thepatient's heart chamber, saline is typically delivered from theirrigation pump 114 to the distal tip 122. Fluid weeps from the distaltip 122 via the closed valves 124 at a low rate (e.g., about 2 ml/min),e.g., during catheter manipulation and mapping, before ablation isinitiated or after ablation is completed.

After being positioned in the desired region of the heart, the ablationcatheter 104 is advanced into contact with the region of the tissue tobe ablated. As discussed above, fluoroscopy can be used to visualize thecontact between the distal tip 122 of the ablation catheter 104 and thepatient's tissue. Due to the conformability of the distal tip 122,contact with the tissue causes the distal tip 122 to deform. Thisdeformation can be clearly viewed under fluoroscopy. The position sensorwithin the distal end region of the catheter shaft 128, in combinationwith the mapping system visualization, can also be used to assist theuser in determining whether the distal tip 122 is properly positioned.In addition, the amplitude of the cardiac electric signal (e.g., ECG)detected by the tip surface electrodes will increase as the electrodecontacts the heart tissue. The user typically advances the catheter 104until the distal tip 122 has deformed by an amount equal to ¼ to ½ ofthe diameter of the distal tip 122 in the undeformed state. Thisdeformation increases the surface area of the distal tip 122 thatcontacts the tissue and thus increases the surface area of the tissueregion that will be ablated. Other methods to determine tip to tissuecontact described in this disclosure can also serve to verify propercatheter placement prior to ablation initiation.

When the user is ready to initiate the ablation process, he or sheactivates the ablation generator 116, causing the ablation generator 116to deliver energy to the ablation electrode 120 on the inner surface ofthe distal tip 122. Before the ablation generator 116 is activated, thespeed of the irrigation pump 114 is also increased to cause the salineto flow at an increased rate (e.g., 15 ml/min to 30 ml/min). Theactivation of the ablation generator 116 and the speed increase of theirrigation pump 114 can be triggered via an input device (e.g., button,knob, touchscreen, etc.) of the catheter interface unit 108 and/or ofthe ablation generator 116. As the saline delivered through the catheter104 exits the open valves 124 in the regions of the distal tip 122 thatare deformed due to contact with the tissue, the energy is transmittedvia the saline to the tissue adjacent the open valves 124, therebyablating that tissue.

In addition to serving as a conduit that carries the energy to thetissue of the patient, the saline also provides a cooling function. Thesaline can, for example, cool the portions of the tissue nearest thedistal tip 122, which tend to receive the lowest cooling due to bloodflow and thus absorb the most heat. The saline can help to prevent thattissue from overheating, potentially leading to steam pop, and can helpto prevent blood interfacing with the ablation energy from coagulating.

As the tissue is being ablated, the signals of the electrodes 146, 148thermistors of the distal tip 122, and a pressure sensor are read by thecontrol unit in the catheter interface unit 108 via the cable bundlesthat extend through the catheter shaft 128. This data can be processedby the control unit in several different ways to assess a state of thedistal tip (e.g., the degree of contact between the distal tip 122 andthe tissue or a shape of the distal tip 122) and to monitor the progressof the lesion being created by the energy.

The thermistors detect the temperatures of their associated outerelectrodes 146 and transmit that temperature data to the control unit ofthe catheter interface unit 108. The control unit of the catheterinterface unit 108 receives the temperature data and uses that data todetermine which of those electrodes 146 are in contact with or in closeproximity to the tissue being ablated. The thermistors associated withthe outer electrodes 146 that are in contact with or in close proximityto the tissue being ablated will detect a greater temperature than theouter electrodes 146 that are farther away from the tissue beingablated. This is because energy is directed towards tissue via thevalves and blood flow cools the tip where it is not in contact withtissue. Thus, the control unit can determine which regions of the distaltip 122 are contacting or nearly contacting the tissue by determiningwhich of the outer electrodes 146 have the highest temperatures.

The control unit can also assess the progress of the lesion beinggenerated based on the temperature data received from the thermistors.The design of the distal tip 122 and its outer electrodes 146 andthermistors, as discussed above, allow for accurate temperature readingsof the outer electrodes 146 in direct contact with the tissue beingablated and thus in conjunction with power, duration, impedance andtissue coupling parameters allow for more accurate assessment of variouscharacteristics, such as size, shape, and depth, of the lesion beingcreated. The various sensors, in combination with the methods by whichthey are driven, interrogated, and/or analyzed can provide informationindicative of the state of the tip. Information indicative of the stateof the tip can be detected by the various sensors described herein, forexample, by the inner and outer electrodes, and can be based onimpedance measurements between the ablation tip and the return electrodeand pressure sensor. The state of the tip can be assessed based on, forexample, its shape and the extent and/or locations of open valves. Thesecharacteristics in turn can be used to assess the level of couplingbetween the catheter tip and tissue, and as a safety mechanismindicating a failure. For example, the location and extent of shapedeformation can indicate a level of tissue contact and/or coupling.Providing this information, in combination with additional information,can aid to verify proper catheter placement prior to ablation onset.During ablation, this information in addition to knowledge of otherparameters such as, for example, temperature, power, and duration, canbe used to assess the dimensions of lesion formation. For example,information related to lesion formation can be collected using thetemperature sensors and electrodes, and can also be computed usinginformation collected by these sensors. In addition, a change in thisinformation can indicate an undesirable event, such as inadvertentcatheter movement of the catheter during ablation.

Current driven across the external and internal electrodes 146, 148 orimpedance values measured using voltages detected across the externaland internal electrodes 146, 148 can be used to determine whether valves124 located near those electrodes 146, 148 are in an open or closedstate. That information can, in certain circumstances, be used todetermine the shape of the distal tip 122. In regions of the distal tip122 in which the shape activated valves 124 are open, a current isdriven between one of the external electrodes 146 and its correspondinginternal electrode 148. As the current is driven between the externalelectrode 146 and its associated internal electrode 148, a detectedvoltage across those electrodes 146, 148 that is above a thresholdvoltage is indicative of a closed valve, while a detected voltage acrossthose electrodes 146, 148 that is below a threshold voltage isindicative of an open valve. In circumstances in which the currentdriven between the external and internal electrodes 146, 148 is notconstant, it can be beneficial to calculate the impedance between theexternal and internal electrodes 146, 148 to determine the state of thenearest valves 124. The impedance can be calculated from the knowncurrent driven between the external and internal electrodes 146, 148 ata given time and the voltage detected across those electrodes 146, 148at that time. A calculated impedance that is above a threshold impedanceis indicative of a closed valve, while a calculated impedance that isbelow a threshold voltage is indicative of an open valve. In addition todetermining which of the various valves 124 are open in this way, thisinformation can also allow the shape of the distal tip 122 to beestimated. In some implementations, particular impedance values (or,e.g., combinations of particular impedance values between variouselectrodes) can correspond to open/closed states of various values. Inthis way, the open/closed states of the values can be mapped to animpedance profile of the electrodes.

The determination in the manner described above of which valves 124 areopen and which valves 124 are closed can also be used for other reasons.For example, this information can be used to confirm that all valves 124within a deformed region of the distal tip 122 that is in contact withtissue are in fact open, as would be expected. A determination that oneor more of the valves 124 in a deformed region of the distal tip 122 hasnot opened can be indicative of an error in either the determination ofthe state of the distal tip 122 or the determination of the valve state.

The internal electrodes 148 alone can also be used to determine theshape of the distal tip 122 and thus to determine whether and to whatextent certain regions of the distal tip 122 are in contact with thetissue. For example, the control unit can cause a current to be drivenfrom one of the internal electrodes 148 to another of the internalelectrodes 148 and the voltage across those electrodes can be monitored.The particular electrodes through which the current is driven can becontrolled using various multiplexing schemes, as described above. Thedistance between those electrodes can be determined based on the voltagedetected. For example, as the distance between two electrodes decreases,the detected voltage across those electrodes will decrease, and viceversa. In this way, by repeating this process across the different pairsof internal electrodes an approximate shape of the distal tip 122 can bedetermined based on the voltage detected across the electrodes 148.

In some implementations, a current is driven from one of the internalelectrodes 148 to another of the internal electrodes 148 while otherinternal electrodes 148 (referred to in this case as passive electrodes)detect a voltage. The voltages detected by the passive electrodes can beused to determine the approximate shape of the distal tip 122 by fittingthe measurements collected by them to either a lookup table or amathematical model mapping these measurements to various shapes.

It should be appreciated that the outer electrodes can also be used todetermine shape in a manner similar to the one described above.

It should further be appreciated that by determining the catheter tipshape, saline volume at the tip can also be estimated as the volume ofthe shape. Furthermore, saline volume can be estimated independently ofthe specific shape using data collected by the various tip electrodes.Saline volume provides an indication of tip to tissue coupling. Thesmaller the volume of saline, the more deformed that tip is andtherefore, the more coupled it is to the tissue surface.

The outer electrodes 146 can also be used to generate unipolar andbipolar electrograms.

Additionally, the impedance between the outer electrodes 146 and thereturn electrode 118 can be used to assess lesion progress. As thetissue is ablated adjacent a particular outer electrode 146, theimpedance between that outer electrode 146 and the return electrode 118decreases. Thus, the measured impedance values between the various outerelectrodes 146 and the return electrode 118 can be used to providefeedback on the ablation lesion. When a constant current is used, adetected voltage across the outer electrode 146 and the return electrode118 is proportional to the impedance and can thus be used to providefeedback on lesion progress. In some implementations, lesion progresscan be assessed simultaneously with tissue ablation. For example, a 500kHz signal can be used for ablation, and a 5 kHz signal can be used toassess lesion progress so that the signals can be distinguished.

The impedance between the ablation electrode 120 and the returnelectrode 118 can also be used to assess lesion progress. As tissue isablated between the ablation electrode 120 and the return electrode 118,tissue impedance decreases and therefore impedance between thoseelectrodes decreases. Thus, the measured impedance values between theablation electrode 120 and the return electrode 118 can be used toprovide feedback on lesion progress. As noted above, when a constantcurrent is used, a detected voltage across the ablation electrode 120and the return electrode 118 is proportional to the impedance. Variousmultiplexing schemes can be used to control which electrodes are usedfor ablation and which electrodes are used for assessing lesionprogress.

Additionally, the signal resulting from the ablation signal (e.g., the500 kHz ablation signal) emanating from the ablation electrode 120 tothe return electrode 118 can be analyzed on inner electrodes 148 andouter electrodes 146. The amplitude and phase of the difference betweenelectrodes 146 and 148 can be analyzed similar to a 4-wire resistancemeasurement. Reduction in amplitude and a phase change are indicative ofimpedance change in nearby tissue, which in itself, is indicative oftissue temperature and lesion progress.

The concentric design of the outer electrodes also allows determiningwhether they are in tissue contact. By driving a current between twoouter electrodes and measuring the impedance between them,electrode-tissue contact can be determined. Since the impedance oftissue is roughly 2.5 times that of blood, there will be approximately a2.5 impedance rise between the concentric electrodes when in contactwith tissue relative to a state where they are largely in blood contact.In order to determine tissue contact, baseline impedance values can besaved when the tip is confirmed not to be in contact with tissue. Thiscan be done guided by fluoroscopy, the shape detection, or other means.This can be done automatically by the software, or initiated by thecomputer operator. Alternatively, typical values can also be stored inthe computer program. Once the impedance value between the twoconcentric electrodes exceeds a certain threshold, for example 1.5 timesbaseline, contact between the electrodes and tissue can be indicated tothe physician.

The control unit of the catheter interface unit 108 can process theabove-discussed data from the thermistors, the internal electrodes 148,the external electrodes 146, and the return electrode 118 in any of thevarious ways discussed above to determine or approximate the shape ofthe distal tip 122 and/or characteristics of the lesion created. Thecontrol unit can then generate and output signals to the display 110 ofthe catheter interface unit 108 that are representative of the shape ofthe distal tip 122 and/or the characteristics of the lesion. The shapeof the distal tip 122 and/or the characteristics of the lesion can thenbe displayed on the display 110 of the catheter interface unit 108. Thephysician can use this image to better understand the type of contactthe distal tip 122 is making with the tissue and the size and shape ofthe lesion being formed.

FIGS. 9 and 10 are examples of screen shots from the monitor of theablation system during an ablation treatment. Referring first to FIG. 9, the monitor displays a graphic representation of the distal tip 122with markings that represent the various electrodes of the distal tip122. Two of those electrodes are surrounded by a marking (e.g., anannular ring of a different color than the displayed electrodes) thatindicates those particular electrodes are in contact with tissue. Insome implementations, for example, the electrodes are colored in blackwhile the surrounding markings are colored in white. However, othercolor schemes and other types of graphical representations canalternatively or additionally be used. The remaining electrodes includeno such surrounding marking, thereby indicating that those electrodesare not in contact with tissue.

The various different regions of the distal tip 122 are displayed indifferent colors, depending on the detected temperatures of thoseregions. In some implementations, for example, the warmest detectedtemperature regions are displayed in red, the coolest detectedtemperature regions are displayed in blue, and regions of intermediatetemperatures are displayed as some relative combination of red and blueor as other colors, such as green and yellow. This graphicalrepresentation of the temperature of the distal tip 122 can also serveas a tool to determine which portions of the distal tip 122 are incontact with tissue as the portions of the distal tip 122 in contactwith the tissue will allow saline (and thus electrical energy) to flowthrough open valves to the tissue, thereby resulting in elevatedtemperatures.

A vertical temperature scale is provided to the left of the graphicalrepresentation of the distal tip 122 in FIG. 9 . In this case, themaximum detected temperature (or a rounded temperature value near themaximum detected temperature) is provided at the top of the scale andthe minimum detected temperature (or a rounded temperature value nearthe minimum detected temperature) is provided at the bottom of thescale. The scale includes multiple different hash marks along its lengththat are visually distinguishable from one another. Typically, forexample, the hash marks are different colors that correspond to thevarious displayed colors on the graphical representation of the distaltip 122. By looking at the maximum and minimum temperatures of thescale, the user can readily determine or estimate the temperatureassociated with each of the different hash marks along the scale. Inthis way, the user can use the scale to determine or estimate thetemperature of tissue or other environment adjacent the variousdifferent regions of the distal tip 122.

In addition to the color gradient describes above, a deformed region ofthe distal tip 122 (e.g., the region of the distal tip 122 that is incontact with tissue) is demarcated by a dashed line. This can furtherhelp the user to visualize the area of tissue contact and thus the areaof the lesion being formed.

In some implementations, the valves of the distal tip 122 are displayedat appropriate locations on the distal tip 122. In such implementations,the valves that are determined to be open can be displayed differentlythan the valves determined to be closed. For example, the open valvescan be displayed in one color while the closed valves are displayed in adifferent color. Alternatively, the valves can be displayed in a waythat represents the way the valves actually look in their closed andopen positions.

As shown in FIG. 9 , a graph is provided beneath the graphicalrepresentation of the distal tip 122 for showing a tissue couplingmetric over time. The tissue coupling metric value at any given timecan, for example, be determined by determining values of the variousouter electrodes. In this case, the electrodes that are determined to bein contact with tissue are assigned a value of 10, while the electrodesthat are not in contact with tissue are assigned a value of 0. Theaverage value across the various outer electrodes can then be determinedand displayed as the tissue coupling metric over time. This value canprovide the user with an indication of the degree of contact between thedistal tip 122 and the patient's tissue. In some implementations, thecontrol unit of the system is also configured to disable ablation untilthe tissue coupling metric reaches or exceeds a predetermined minimumvalue that indicates sufficient contact between the distal tip 122 andthe patient's tissue. The predetermined minimum value can, for example,be 4 on the scale of 0 to 10.

Still referring to FIG. 9 , the maximum temperature across the differentsensors, power, impedance, and current associated with the ablationsystem is also displayed beneath the graphical representation of thedistal tip 122.

FIG. 10 shows an alternative arrangement for the display of the ablationsystem. This screen displays much of the same information displayed inthe screen shot of FIG. 9 . However, rather than being arrangedvertically along the screen, that information is displayed horizontallyalong a top region of the screen. A status bar above that data indicatesthe status of the ablation system. In this example, the status barindicates that the system has been performing ablation for 12 seconds.The display illustrated in FIG. 10 also includes a graph that shows theprogression of the detected temperature, power, impedance, and currentover time.

An image representing the shape of the distal tip 122 andcharacteristics of the lesion during treatment can also be displayed onthe monitor. The physician can use this information to confirm that thedistal tip 122 remains in proper contact with the tissue throughout thetreatment. The physician can, for example, use this information to helpensure that the distal tip 122 is deformed (e.g., by an amount equal toat least ¼ to ½ of its diameter in its undeformed state) throughout thetreatment. The depiction of temperature within the treated tissue (e.g.,by the use of a color gradient representing a range of temperatures orsome other graphic representation of temperature) can also help thephysician to understand the area and depth of the tissue that is beingablated.

In some implementations, the image or video displayed on the display 110depicts the regions of the tissue according to their temperature usingan isothermal map. For example, darker regions of the image canrepresent hotter tissue regions, while lighter regions represent coolertissue regions. Alternatively, different colors can be used to representthe different tissue temperatures. For example, red regions of the imagecan represent hotter tissue regions, while blue regions of the imagerepresent cooler tissue regions. The physician can use this informationto better understand the size, particularly the depth, of the lesionbeing created. Thus, this can help to ensure that lesions of a desireddepth are generated during the treatment. When data from the sensors ofthe ablation catheter 104 are combined with data collected form therecording/mapping system, these graphical representations of the distaltip 122 and the tissue being ablated can further ensure that desiredlevels of energy are reaching the specific regions of tissue intended tobe ablated. This can be particularly beneficial when the region oftissue to be ablated is thick.

Since the area of contact with the endocardium is actively cooled withirrigation, permanent lesions can sometimes not form on the endocardium.This effect is referred to as endocardial sparing and is undesirablewhen applying a permanent ablation lesion. The following describes atitration of power and flow in order to maximize lesion size and avoidendocardial sparing. In the first phase, lasting approximately 30 s,high (e.g. 15-30 mL/min) flow could be used with a lower power setting(e.g. 20 W). This phase helps heat the immediate endocardial tissue,reducing its impedance, thus allowing deeper penetration of power in thesecond phase. Once heating and impedance drop is accomplished, a secondphase, lasting approximately 30 s, with the same flow and higher power(e.g. 40 W) can be applied. In this phase the highest power and the mostenergy is delivered, making this phase primarily responsible for thelesion's eventual depth. Subsequently, a third phase targets endocardialtissue lasting approximately 30 s, where both power and flow are lowered(5-10 mL/min and 20 W) is entered. Due to the lower flow, theendocardium receives less cooling and is more likely to be included inthe permanent lesion. In order to avoid steam pop and char formation,power is also lowered in this phase. The transition between the phasescan be done suddenly (e.g. in a single step) or gradual (e.g. over ashort period of time). This sequence in its entirety can be programmedin advance into the ablation generator, or catheter interface unit andimplemented by the system. Alternatively, this sequence can be manuallyimplemented by hospital staff as the lesion is delivered. While specifictime periods, power settings, and flow settings have been described forthe ablation phases, others could be used.

While certain implementations have been described above, otherimplementations are possible. For example, while the thermistors of thedistal tip 122 have been described as being attached to portions of theflexible printed circuit 154 opposite the central conductive components150 of the various outer electrodes 146, the thermistors canalternatively or additionally be attached to portions of the flexibleprinted circuit 154 opposite the annular conductive components 152 ofthe outer electrodes 146. The thermistors can alternatively be directlyconnected to one of the conductive components 150, 152 of the outerelectrodes 146 (e.g., via openings formed in the flexible printedcircuit 154).

In addition, while the outer and inner electrodes 146, 148 and, in somecases, the thermistors have been described as being attached to discreteflexible circuit pads, in certain implementations, the outer and innerelectrodes 146, 148 and the thermistors are attached to flexible printedcircuit strips that extend from the catheter shaft along the distal tip.These strips could themselves be discrete elements, or branches of asingle flexible circuit.

Various forms of thermistor and thermocouples can be implemented. Forexample, rather than discrete components, these can be applied to theflexible printed circuit as thin film or ink applied as part of theflexible printed circuit manufacturing process. Furthermore, rather thanon the flexible printed circuit, these elements can be applied directlyto the distal tip. For example, the thermistors and thermocouples couldbe formed directly using appropriate thermistive or conductivematerials, e.g., conductive inks, on the distal tip.

While external electrodes have generally been described as circularand/or concentric, other shapes can be used and/or relative locationscan be used. For example, the electrodes could be oval or rectilinear,or positioned in close, but not concentric, proximity. In some examples,the external electrodes can be individual electrodes and/or individualparts (e.g., pieces of metal, assembled on the distal tip.)

While the ribs of the distal tip 122 have been described as beingcircumferentially offset from the slits, in certain implementations, theribs are aligned with the slits.

Additionally, while the distal tip 122 has been described as includingshape activated valves that include three slits formed in sidewalls thatform a tetrahedral recess in the body of the distal tip, other types ofshape activated valves can alternatively or additionally be used. Forexample, a greater number of slits (e.g., six slits) or a smaller numberof slits (e.g., one slit or two slits) can be used to form the valves.In addition, the slit or slits can be formed in recesses having shapesdifferent than the tetrahedral recesses described above. In someimplementations, the slit or slits are formed in portions of the body ofthe distal tip that are not recessed at all. Several examples of distaltips that include different types of shape contact valves and that canbe used on the ablation catheter 104 in place of the distal tip 122described above will now be described.

As shown in FIGS. 11 and 12 , a distal tip 222 includes hemisphericaldimples or recesses 236. For simplicity, only one of the recesses 236 inthese figures is illustrated as including slits 244 for forming shapeactivated valves 224. However, it should be understood that each of therecesses 236 would typically include slits for forming shape activatedvalves. The recesses 236 include three slits 244 that extend outwardlyfrom a center point in much the same way as the slits 144 of the distaltip 122 discussed above. The slits 244 are circumferentially spacedapart from one another by about 120 degrees. As shown in FIG. 12 , ribs242 extend between the inwardly extending hemispherical projections 240of the distal tip 222. The ribs 242 are circumferentially spaced apartfrom one another by about 120 degrees and are circumferentially spacedfrom the nearest slits 244 by about 60 degrees. In much the same way asthe ribs 142 described above with respect to the distal tip 122, theribs 242 help to provide the valve walls with sufficient rigidity tomaintain their shape during local deformations, resulting in valveopening. Any of the various manufacturing techniques described abovewith respect to the distal tip 122 can be used to form the distal tip222.

While the distal tips discussed above have ribs that extend inwardlyfrom the inner surfaces of those distal tips, the distal tips canalternatively include no such ribs. As an example, the distal tip 222illustrated in FIGS. 11 and 12 can alternatively be formed without ribs.In some implementations, this version of the distal tip is molded withhemispherical projections that extend outwardly from the outer surfaceof the distal tip. After forming slits in those outwardly extendingprojections, the distal tip can be inverted (i.e., turned inside out).By inverting the distal tip in this way, the inner surface of theresulting inverted distal tip will be in compression since its internalcircumference will be slightly smaller than its initial outercircumferences when it formed for the outer surface of the pre-invertedtip. This compression can function to bias the valves to a closedposition, making it less likely that liquid will leak through the closedvalves during use.

In addition, while each of the distal tips described above includerecesses that extend inwardly from the outer surface of those distaltips, the distal tips can alternatively include no such recesses. Asshown in FIGS. 13 and 14 , for example, a distal tip 322, which includesa slightly thicker wall than some of the distal tips discussed above,includes smooth inner and outer surfaces with slits 344 extendingtherethrough. The wall thickness of the spherical body portion of thedistal tip can range from 0.15 mm to 1.5 mm. As showed in FIG. 14 , theslits 344 flare inward from the inner surface towards the outer surfaceof the distal tip, as manufactured. Prior to attaching the distal tip322 to the ablation catheter shaft 128, the distal tip can be inverted(i.e., turned inside out). Due to the slight change in circumference ofthe surface that initially forms the outer surface of the distal tip 322and ultimately forms the inner surface of the inverted distal tip 322used in the ablation catheter 104, the inner surface of the inverteddistal tip 322 experiences compression forces that bias the valves 324to a closed position. As discussed above, this helps to prevent liquidfrom leaking from the closed valves 324 during use.

FIG. 15 illustrates a distal tip 422 that is similar to the distal tip322 of FIGS. 13 and 14 in that a relatively thicker wall is utilized forvalve function. Intersecting cross slits 444 are formed in the wall ofthe distal tip 422. The slits 444 cut through from the inner surface tothe outer surface of the distal tip 422. The conical feature at theouter surface of the distal tip 422 is positioned to leave an open holefor fluid passage when a radially inward force is applied to the outersurface of the distal tip 422. For example, the radius of curvature ofthe outer surface will decrease, thereby placing the outer surface incompression. The material at outer edge of the cone will bear thecompressive load of the outer surface during bending. At the same time,tension is created at the inner surface of the distal tip 422, causingthe initially narrow slit regions (e.g., closed slit regions) to widen,thereby opening the valve 424. In other words, as the structure islocally pressed inward, the valves will pivot where the slits cometogether at the edge of the reliefs at the outer surface. The conicalvoids will ensure that a hole is open at the outer surface to allowfluid to pass as the slits at the inner surface spread apart.

FIG. 16 illustrates another distal tip 522 similar to the distal tips322 and 422 discussed above. The distal tip 522 includes smooth innerand outer surfaces, and the wall of the distal tip 522 includes multiple3-legged slits 544 (also referred to as trifurcations) that form shapeactivated valves 524. The slits 544 within each of the slit groupingsare circumferentially spaced from each other by about 120 degrees. Theslit groupings are arranged in a manner such that hexagonal regions 550that are free of slits are formed between many of the adjacent slitgroupings. As radially inward forces are applied to the outer surface ofthe distal tip 522, these hexagonal regions 550 tend to remain in theirbaseline nominal curvature. However, neighboring hexagonal regions 550will move relative to one other while retaining their nominalconfigurations. This relative movement of the neighboring planar regions550 causes the valves 524 to open in response to deformation of thedistal tip.

Although not shown in FIG. 16 , the distal tip 522 can includeprojections that extend outwardly from the outer surface of the distaltip 522 in the hexagonal regions 550 between the groupings of slits 544.The projections can amplify the extent of displacement of the hexagonalregions 550 in response to a radially inward force applied to the outersurface of the distal tip 522. This can facilitate opening of the valves524 in response to such forces.

FIG. 39 illustrates a distal tip 2522 that is very similar in design tothe distal tip 522 of FIG. 16 . The distal tip 2522 includes a smoothouter surface, and the wall of the distal tip 2522 includes multiple3-legged slits 2544 (also referred to as trifurcations) that form shapeactivated valves 2524. Unlike the distal tip 522 of FIG. 16 , the distaltip 2522 includes raised regions 2542 that extend between intersectionpoints of neighboring 3-legged slits 2544. The raised regions 2542 arehexagonal in shape and have a greater wall thickness than the otherregions of the wall of the distal tip 2522. As a result, the raisedregions 2542 provided greater stiffness to regions of the wall extendingbetween neighboring 3-legged slits 2544. This construction helps toensure that, as radially inward forces are applied to the outer surfaceof the distal tip 2522, the portions of the wall including the raisedregions 2542 maintain their shape while moving relative to one other toopen the valves 2524 formed by the 3-legged slits 2544. The distal tip2522 can also include projections (not shown in FIG. 39 ) that extendoutwardly from the outer surface of the distal tip 2522 in regionsbetween the groupings of slits 2544 to allow for fluid communicationbetween neighboring valves 2524. Although FIG. 39 shows the raisedregions on the inside surface of the tip, the raised regions could besituated on the external surface to achieve similar effects.

While certain distal tips described above, such as the distal tip 122illustrated in FIGS. 2-5 , include recessed regions and have generallysmooth outer surfaces between the recessed regions, those smooth outersurfaces can alternatively be formed to define channels that permitfluid flow therethrough. These channels could have a U-profile (orV-profile) and replace the valve ribs, functionally. FIGS. 40 and 41illustrate a distal tip 2622 that includes U-shaped projections 2642that extend between valve recesses 2636 that have the same generalconfiguration as the recesses 136 described above with respect to thedistal tip 122 illustrated in FIG. 5 . The projections 2642 operate inmuch the same way as the ribs 142 of the distal tip 122 described above.In particular, the projections 2642 provide added stiffness to theregions of the distal tip 2622 between the recesses 2636 and thus assistwithin opening of valves 2624 within those recesses 2636. Each of theprojections 2642 includes opposing surfaces forming a channel 2645 witha U-shaped profile that extends between neighboring recesses 2636. Thisdesign can help to ensure that saline exiting open valves 2624 in therecesses 2636 is able to flow out of the distal tip 2622 and along thetissue by preventing the tissue from forming a complete seal with theouter surface regions surrounding the open valves 2624.

Furthermore, these channels 2645 can be advantageously used when havinga conformal tip with holes rather than valves. In this scenario,irrigation holes are connected with a network of channels guaranteeingthat fluid irrigation is still active in regions where the tip ispressed against tissue.

Other techniques can also be used to help prevent fluid stasis in theregion of tissue contact. As show in FIG. 17 , for example, a distal tip622 has a very similar construction to the distal tip 122 discussedabove. Unlike the distal tip 122, the distal tip 622 illustrated in FIG.17 includes projections 660 that extend outwardly from regions of theouter surface between adjacent recessed regions 636. These projections660 cause separation between the patient's tissue and portions of theouter surface of the distal tip 622 that surround the recessed regions636, which form the shape activated valves 624. As a result, theprojections 660 help to ensure that fluid is able to exit the openvalves 624 and flow between the outer surface of the distal tip 622 andthe patient's tissue as opposed to simply stagnating within the recessedregions 636 associated with the open valves 624. In addition, theprojections 660 can amplify deformation of the valves 624 and thusfacilitate opening of the valves 624 in regions of the distal tip 622contacted by tissue. The projections 660 can also increase frictionbetween the distal tip 622 and the patient, leading to improvedmechanical stability and reduced movement of the catheter duringablation delivery.

While the distal tips described above include generally linear slits,various other shaped slits and types of valves can be used. As shown inFIG. 18 , for example, a distal tip 722 includes multiple U-shaped slits744 that form flaps 738 that act as valves 724 around the distal tip722. Projections 760 extend outwardly from the outer surfaces of theflaps 738. The projections 760 help to ensure that the flaps 738 moveinwardly to a greater extent than neighboring flapless regions of thedistal tip 722 when a radially inward force is applied to the outersurface of the distal tip 722. The projections 760, therefore,facilitate opening of the valves 724 in response to inwardly appliedforces. The resiliency of the flaps 738 causes the flaps 738 to returnto their original positions upon removal of the radially inward forces.Therefore, the valves 724 have the capability of reclosing if the userneeds to reposition the distal tip 722 such that the contact points ofthe distal tip 722 change during use.

In order to help ensure that tissue adjacent the flaps 738 do notcontact and create a seal with regions of the outer surface surroundingthe valves 724, which can make it difficult for fluid to be distributedto other tissue regions, additional smaller projections (not shown) canextend from the flapless regions between neighboring valves 724. Thesesmaller projections help to ensure that certain portions of the tissueremain spaced from the surface of the distal tip 722 such that fluid canflow between the tissue and the distal tip 722 rather than flowingelsewhere.

FIGS. 19 and 20 illustrate a distal tip 822 that includes hemisphericalprojections 860 that extend outwardly from the outer surface of the tip822 and hemi-spherical recesses 836 that extend inwardly from the outersurface of the tip 822. Valves 824 are formed by slits 844 (shown inFIG. 20 ) that extend through the portions of the body forming theprojections 860 and the recesses 836. The slits 844 in the recesses 836operate in a manner similar to the slits 144 of the distal tip 122described above. Specifically, as the wall of the distal tip 822 isdeformed radially inward and forms a flat or concave shape, tensioncreated at the inner surface of the distal tip 822 widens the slits 844in the recesses 836, thereby opening those valves 824. In contrast, theprojections 860 in those flattened or concave regions of the tip 822tend to experience compressive forces, which cause the slits 844 toclose tighter. Those valves 824 behave in the opposite manner when thetip 822 is deformed in a manner to take on a more convex shape. FIG. 20shows the distal tip 822 being advanced distally into tissue such that aradially inward force is applied to a distal end region of the tip 822by the tissue. As a result, the distal end region of the tip 822 hasmoved proximally and has become flat or concave in shape. The valves 824of the recesses 836 in the flat or concave region have been opened dueto tensile forces at the inner surface of the distal tip 822 wideningthose slits 844, while the valves 824 of the projections 860 in the flator concave region have been closed due to compressive forces at theouter surface of the distal tip 822 narrowing those slits 844. At thesame time, a circumferential region of the tip 822 at which the tip 822transitions from its normal convex configuration to the deformed flat orconcave configuration has taken on an even more convex shape than theoriginal configuration. As a result, the valves 824 of the projections860 in the circumferential region have been opened due to tensile forcesat the outer surface of the distal tip 822 widening those slits 844,while the valves 824 of the recesses 836 in the circumferential regionhave been closed due to compressive forces at the inner surface of thedistal tip 822 narrowing those slits 844. Thus, providing valves 824 inboth the recessed regions 836 and the projections 860 of the distal tip822 can help to ensure that saline is delivered via open valves 824 toall regions of the tissue that are in contact with or near contact withthe distal tip 822.

In some implementations, additional force-activated structures can bepositioned adjacent valve flaps of the distal tip to help preventleaking from closed valves while permitting fluid to escape via openedvalves. Referring to FIG. 21 , for example, a distal tip 922 hasmultiple flap valves 924 formed in it side wall. The flap valves 924 canhave constructions similar to the various valves described above. Forexample, the body of the distal tip 922 can include one or more slitsthat form valves that can be opened upon deformation of the distal tip922. The distal tip 922 also includes an umbrella valve 970 associatedwith each of the flap valves 924 formed in the body of the distal tip922. The umbrella valves 970 include a sealing portion 972 disposedinside the distal tip 922 and a projection 974 that is connected to thesealing portion 972 and extends outwardly from the outer surface of thedistal tip 922. The umbrella valves 970 are displaceable with respect tothe wall of the distal tip 922. The umbrella valves 970 are also biasedto a position in which the sealing portion 972 is pressed against aninner surface of the distal tip 922 to hold the associated flap valve924 in a closed position. They are biased in this way primarily by theelasticity of the material from which they are constructed incombination with internal pressure within the distal tip 922 resultingfrom irrigation. In some examples, they are also biased by a compliant,elastic member (not shown) that attaches the valve element to the tip.The elastic member could in some implementations be part of the tip,itself. Upon being contacted by tissue, as schematically shown in FIG.21 , the projection 974 and the sealing portion 972 of the umbrellavalve 970 slide radially inwardly. As the sealing portion 972 moves awayfrom the inner surface of the distal tip 922, the flap is free to alsomove radially inward to open the flap valve 924. The use of suchumbrella valves 970 in combination with the flap valves 924 of the typediscussed above can help to reduce (e.g., minimize) the amount of salinethat is allowed to escape from the distal tip via closed flap valves 924during a treatment.

While only the distal tip 122 has been explicitly described as having astructure that provides added support in the proximal region of the tipto prevent deformation of the proximal region of the tip in response toproximal forces applied to the distal region of the tip, it should beunderstood that each of the various other distal tips described hereincan include a similar proximal support.

The various distal tips described herein can alternatively oradditionally include various other types of proximal support structuresthat help to prevent the proximal region of the distal tip fromdeforming proximally due to a proximal force applied to the distalregion of the tip or from excessive bending as a result of a lateralload. For example, as an alternative to or in addition to providing athickened wall along the proximal end region of the distal tip, theproximal end region of the distal tip can be formed of a more rigidmaterial than the distal region of the distal tip.

FIG. 22 illustrates a distal tip 1022 that includes a conical supportstructure 1080 extending between a neck 1030 of the distal tip 1022 anda proximal end region of a spherical body 1032 of the distal tip 1022.The conical structure 1080 can be a solid structure that acts much likea thickened wall region of the distal tip 122 discussed above.Alternatively, the conical support structure 1080 can be a hollowmember, which can reduce the total amount of material required to formthe distal tip. In either case, the conical support structure 1080 canbe either integrally formed with the neck 1030 and body 1032 of thedistal tip 1022 or can be separately formed and then attached (e.g.,thermally or adhesively bonded) to the neck 1030 and body 1032 of thedistal tip 1022.

Other types of support structures can alternatively or additionally beused to limit deformation of the proximal end region of the distal tip.In certain implementations, for example, the proximal end region of thedistal tip includes strengthening ribs. FIG. 23 , for example,illustrates a distal tip 1122 including external support ribs 1180 thatextend from a neck 1130 of the distal tip 1122 to a proximal end regionof a spherical body 1132 of the distal tip 1122. The distal tip 1122typically includes three or four support ribs 1180 that are equallyspaced (e.g., spaced by about 120 degrees or about 90 degrees) about thecircumference of the spherical body 1132 of the distal tip 1122.Although the support ribs 1180 are illustrated as solid members, theycan alternatively be formed as hollow members to reduce the amount ofmaterial required to form the support ribs 1180.

FIG. 24 illustrates a distal tip 1222 that includes multiple ribs 1280that extend along the outer surface of the proximal end region of aspherical body 1232 of the distal tip 1222. In certain implementations,the ribs 1280 are formed of the same material as the spherical body 1232of the distal tip 1222. In such implementations, the increased thicknessof that material in the regions including the ribs 1280 provide theproximal end region of the tip 1222 with increased rigidity. In otherimplementations, the ribs 1280 are formed of harder materials and areattached (e.g., thermally, adhesively bonded or molded) to the sphericalbody 1232 of the distal tip 1222. The use of harder materials to formthe ribs 1280 can ensure that sufficient rigidity is imparted to theproximal end region of the distal tip 1222 while limiting the overallthickness of the proximal end region of the distal tip 1222.

While the distal tips 1122, 1222 illustrated in FIGS. 23 and 24 includesupport ribs that extend along the outer surfaces of those tips, thesupport ribs can alternatively extend along the inner surfaces of thetips or can be embedded or encapsulated within the material of thedistal tip. FIGS. 25 and 26 , for example, illustrate perspective andcross-sectional views, respectively, of a distal tip 1322 includingsupport ribs 1380 that extend from an inner surface of the distal tip1322. These support ribs 1380 typically extend along ⅓ to ⅔ (e.g., ½) ofthe length of the distal tip 1322. The distal tip 1322 typicallyincludes three or four support ribs that are equally spaced (e.g.,spaced by about 120 degrees or about 90 degrees) about the circumferenceof a spherical body 1332 of the distal tip 1322. Because the ribs 1380are positioned inside the distal tip 1322, the outer surface of thedistal tip 1322 is free of projections, as shown in FIG. 25 .

In some implementations, support structures are formed as separatecomponents from the distal tips described herein and then attached tothe distal tip to support desired regions of the tips. As shown in FIGS.42 and 43 , for example, a support structure 2780 is configured to fitover a neck 2730 of a distal tip 2722 to support a proximal end regionof a spherical body 2732 of the distal tip 2722. The support structure2780 includes multiple fingers 2782 that extend radially and distallyfrom the distal end of a tubular member 2784. The support structure 2780can be slid onto the neck 2730 of the distal tip 2722 and then attachedto (e.g., thermally or adhesively bonded to) the neck 2730 and/or thespherical body 2732 of the distal tip 2722. Alternatively oradditionally, the support structure 2780 can be attached to or axiallyfixed relative to the distal end region of the catheter shaft to whichthe distal tip 2722 is attached. The fingers 2782 and the tubular member2784 of the support structure 2780 are more rigid than the wall of thedistal tip 2722 and/or their combined stiffness with the wall whenassembled is sufficient to prevent undesired deformation or deflectionof the tip. The support structure 2780 can, for example, be formed of aharder material than the wall of the distal tip 2722 and/or can have agreater thickness than the wall of the distal tip 2722. Due to therigidity of the support structure 2780, the support structure 2780 canhelp to prevent the proximal end region of the distal tip 2722 fromdeforming in response to a proximally applied force or a sideways forceapplied to the distal tip 2722.

FIG. 27 illustrates a distal tip 1422 that includes three flexibleprinted circuit fingers 1480 that extend along and are attached to theouter surface of a spherical body 1432 of the distal tip 1422.Stiffening strips 1482 are attached to the outer surfaces of theflexible printed circuit fingers 1480 to provide structural support tothe proximal end region of the tip 1422. The assemblies of the fingers1480 and strips 1482 are approximately equally spaced (e.g., spaced byabout 120 degrees) about the circumference of the spherical body 1432 ofthe distal tip 1422.

In some implementations, the stiffening strips 1482 are formed of asuperelastic material, such as Nitinol, which can experience significantlevels of strain without permanent deformation. As a result of thisproperty, the stiffening strips 1482 formed of a superelastic materialcan be compressed while the distal tip is held in its collapsedconfiguration and then reliably return to their original curved shape asthe distal tip is allowed to expand. Other materials from which thestiffening strips 1482 can be formed include metals (e.g., stainlesssteel) and polymers (e.g., polyimide or polyether ether ketone (PEEK)).The printed flexible circuit fingers 1480 can be formed of any ofvarious different materials that are typically used for forming suchstrips.

Outer electrodes 1446 including concentric conductive members 1450, 1452of the type described above with respect to the distal tip 122 areattached to the outer surfaces of the flexible printed circuit material.Inner electrodes in the form of metal pads are attached to the innersurfaces of the flexible printed circuits fingers 1480 and are exposedto the interior of the distal tip 1422. Thermistors are attached to theinner surfaces of the flexible printed circuit fingers 1480, oppositethe outer electrodes, and can be used to detect the temperature of theirassociated outer electrodes.

Referring to FIG. 28 , a distal tip 1522 includes a flexible printedcircuit finger 1580 that extends along the proximal end region of aspherical body 1532 of the distal tip 1522. A patterned layer 1582 ofstiffening material is applied to the finger 1580. Specifically, thematerial is applied to the flexible printed circuit material in multiplediscrete segments 1584 that increase in width as they extend away fromthe flexible printed circuit material to provide asymmetrical bendingbehaviors. In the illustrated implementation, the segments 1584 are inthe shape of trapezoids, but any of various other shapes that are wideralong a top edge than along a bottom edge can be used. This arrangementallows for a radial inward force (i.e., a downward force in theillustrated view) that is applied to the proximal end region of thedistal tip 1522 (i.e., the region of the distal tip 1522 along which theflexible printed circuit fingers 1580 and stiffening segments 1584extend) to inwardly deflect the proximal end region of the distal tip1522. As a result of this inward force, the discrete segments 1584 ofstiffening material will be spaced apart. In contrast, the discretesegments 1584 of stiffening material will limit (e.g., prevent) theproximal end region of the distal tip 1522 from deflecting outward(e.g., in response to a proximal force applied to the distal end regionof the distal tip 1522). Such a force would compress the discretesegments 1584 of stiffening material together. Due to the closeproximity of the neighboring discrete segments 1584 and the stiffness ofthose segments, very little movement in the radial outward direction(i.e., in the upward direction in the illustrated view) will be allowed.In some cases, as few as one trapezoid (or other functionally equivalentshape) and one rigid element near the neck provides asymmetric bendingbehavior.

While the stiffening strips or segments 1482, 1582 of the distal tips1422, 1522 illustrated in FIGS. 27 and 28 have been described as beingattached to flexible printed circuit fingers 1480, 1580, the stiffeningstrips or segments 1482, 1582 can alternatively be integrally formedwith the flexible printed circuit fingers 1480, 1580. In otherimplementations, no stiffening strips are added to the flexible printedcircuit fingers. In such implementations, for example, portions of theflexible printed fingers extending along the proximal end region of thedistal tip are simply increased in thickness to provide added support tothe proximal region of the distal tip.

The various distal tips described herein can also include stiffeningstrips that are independent of any flexible printed circuit fingers thatthose tips might have. The distal tip can, for example, include separatestiffening strips that extend along the outer surface of the proximalend region in much the same way that the flexible printed circuitfingers 1480 extend along the outer surface of the distal tip 1422illustrated in FIG. 27 . The stiffening strips can be attached (e.g.,thermally or adhesively bonded) to the outer surface of the distal tipor can simply rest along the outer surface of the distal tip in anunattached configuration. The stiffening strips could alternativelyextend along and attach to the inner surface of the distal tip or couldbe embedded or encapsulated within the wall of the distal tip. Any ofthe various materials discussed above with respect to the stiffeningstrips 1482 illustrated in FIG. 27 can be used to form these stiffeningstrips.

As an alternative to or in addition to stiffening members extendingalong the surface of the distal tip, tensioning tethers can be usedlimit the amount of radial outward deflection or deformation that thedistal tip can experience. As shown in FIGS. 29 and 30 , for example, astiff member 1690, which is attached at its proximal end region to acatheter shaft, extends into the interior of a spherical body 1632 of adistal tip 1622, which is also attached at its proximal end region tothe catheter shaft. Each of multiple tethers 1680 is anchored at one endto a distal end region 1691 of the stiff member 1690 and at its otherend to the distal tip 1622 (e.g., the inner surface of the distal tip1622). The tethers 1680 are in light tension when the distal tip 1622 isin its normal, undeformed configuration. The tethers 1680 can withstandhigher tensile forces, however, in the event that a radially outwardforce is applied to a portion of the distal tip 1622 to which the tether1680 is attached. The tethers 1680 are typically in the form of a wireor string and can be formed of any of various different materials,including metals (e.g., stainless steel) and polymers (e.g., Kevlar).Braided or solid core wires can be used.

FIG. 30 illustrates one side of the distal tip 1622 being inwardlydeformed by a radially inwardly directed contact pressure. Because thetethers 1680 have a low buckling stiffness and are thus very complaintin compression, the tethers 1680 in the right hemisphere of the distaltip 1622 (i.e., the hemisphere to which the contact force is beingapplied) have buckled, allowing the inward deformation of the distal tip1622. The resulting outward forces applied to the opposite side of thedistal tip 1622 have placed the tethers 1680 in the left hemisphere intension. These tethers 1680 limit (e.g., prevent) radial outwardmovement of the distal tip 1622 and thus helps to ensure thatdeformation of the distal tip 1622 occurs in those regions of the distaltip 1622 that are in contact with tissue.

While only four tethers are illustrated in FIGS. 29 and 30 , it shouldbe understood that more tethers can be used. Further, the tethers can beattached to any regions of the balloon for which outward deformation isundesired. In some examples, the tethers are formed from electricalwires extending to various electrodes and/or sensors of the ablationcatheter.

While certain distal tips have been described as including conductiveink in some implementations other types of conductive layers can beused.

While the ablation electrode has been described in the form of acontinuous conductive layer applied to the inner surface of the distaltip any of various other patterns can alternatively be used. In someimplementations, the ablation electrode occupies a smaller area of thedistal tip to provide increased resistive heating of the saline withinthe distal tip. As shown in FIG. 31 , for example, the inner surfaces ofproximal and distal end regions of a distal tip 1722 each include anablation electrode in the form of a conductive layer 1720, but a centralregion 1721 of the distal tip 1722 is free of conductive materialforming two discrete electrodes. Each of the two discrete regions havingthe conductive layer 1720 is connected to its own dedicated wire forreceiving electrical energy from the ablation generator 116. Thisarrangement can be used to heat the saline to a desired temperature withone of the electrodes (e.g. the proximal one) before the saline exitsthe distal tip 1722.

During use, saline is delivered via an irrigation lumen 1794 of thecatheter shaft to the interior of the distal tip 1722. When it isdesired to heat the saline, the energy can be applied to a proximalregion of the conductive layer 1720 only. As the current passes throughthe saline from a proximal end region of the distal tip 1722 toward adistal end region of the distal tip 1722 (e.g., when valves at thedistal end region of the distal tip 1722 are opened due to contact withtissue), the impedance caused by the saline results in resistive heatingthat raises the temperature of the saline. When it is desired to ablatetissue with less heating of the saline in the distal tip 1722,electrical energy can be applied to both a proximal and a distal regionsof the conductive layer 1720. These schemes can be used, for example, toavoid endocardial sparing as previously described.

As shown in FIG. 31 , the ablation catheter is equipped with atemperature sensor 1790 (e.g., thermistor) that can be used to monitorthe temperature of the saline within the distal tip 1722. Temperaturedata can be received by the control unit in the catheter interface unit108 from the catheter via wires extending through the catheter shaft,and the control unit can cause the ablation generator 116 to deliverelectrical energy in a manner to achieve the desired saline temperature.

As an alternative to or in addition to using two discrete regions eachhaving an ablation electrode to heat the saline within the distal tip,other heating techniques can be used. As shown in FIG. 32 , for example,an ablation catheter includes a distal tip 1822 having an ablationelectrode 1820 on its inner surface in the form of conductive coating. Aheating element 1892 is positioned within the catheter shaft along anirrigation lumen 1894 leading to the distal tip 1822 and can be used toheat the saline flowing into the distal tip. The control unit of thecatheter interface unit 108 can control the heating element 1892 (i.e.,can control the amount of electrical energy applied to the heatingelement 1892) based on temperature data received from the temperaturesensor 1890. The heating element 1892 can, for example, be activatedonly when it is desired to heat the saline.

While the above-described distal tips include ablation electrodes in theform of conductive layers, other types of ablation electrodes canalternatively or additionally be used with any of those distal tips. Incertain implementations, for example, the material of the spherical bodyand the neck of the distal tip is loaded with an electrically conductivematerial such that material of the spherical body and the neck cantransmit energy to saline within the distal tip. In certainimplementations, for example, the distal tip is formed of a polymer thatis loaded with electrically conductive particles. Examples of suitablepolymers include silicone, SEBS, polyurethane, Nylon, and PEBAX.Examples of suitable electrically conductive particles include silverparticles, glass coated silver particles, carbon particles, and goldparticles. To prevent the energy from being transmitted directly to theblood or tissue of the patient outside the distal tip by theelectrically conductive material of the spherical body and the neck, theouter surface of the distal tip can be coated with an electricallyinsulating material, such as silicone, parylene, or polyurethane.

In some implementations, as shown in FIG. 33 , a rod-shaped ablationelectrode 1992 extends distally from the distal end of the cathetershaft and into the interior of the distal tip 1922. The saline(indicated by dashed arrows in FIG. 33 ) exits the irrigation lumen 1994of the catheter shaft and fills the interior of the distal tip 1922. Asthe distal tip fills with saline, the saline will contact the ablationelectrode 1992, allowing energy to be transmitted from the ablationelectrode 1992 to or through the saline. This arrangement typicallyresults in the ablation electrode 1992 being positioned close to thetissue being ablated, which can reduce the impedance to tissue and allowmore power to be delivered. Various schemes can be employed to increasethe surface area of the ablation electrode 1992 and therefore reduce itsimpedance while keeping its volume low. For example, the surface area ofthe rod or wire can be increased by adding exposed branches or strandsof wire or coiling an exposed length of it within the tip.Alternatively, the electrode could be comprised of a convoluted strip orsurface of conductive material.

While the ablation electrode 1992 has been described as being fixedlyattached to the distal end of the catheter shaft, the ablation electrodecan alternatively be axially displaceable within the catheter shaft andthe distal tip. In some implementations, for example, the ablationelectrode can be integrated with a push rod that is used to collapse thedistal tip prior to insertion of the distal tip into the patient. Theablation electrode can, for example, be in the form of a bulbous elementattached to the distal end of the push rod. This configuration canprovide the ablation electrode with an increased surface area, whileusing the relatively thin rod to deliver the energy to the ablationelectrode. This can help to limit the total volume of space within thedistal tip occupied by the push rod and the ablation electrode.

While various types of ablation electrodes have been described, othertypes of ablation electrodes can be used. In certain implementations,for example, the ablation electrode can be implemented as a collectionof thin conducting threads that either extend along the irrigation lumenand/or extend into the interior region of the distal tip.

While the ablation electrodes of many of the distal tips above have beendescribed as being positioned within the distal tip, the ablationelectrode can alternatively or additionally be located in other regionsof the ablation catheter. FIG. 34 , for example, illustrates an ablationelectrode 2092 positioned along an irrigation lumen 2094 of the cathetershaft. The ablation electrode 2092 is in the form of a tube that forms aportion of the irrigation lumen 2094. The ablation electrode 2092 can beformed of one or more electrically conductive materials, such asplatinum, platinum-iridium alloy, gold, or stainless steel. The salineflowing through the lumen 2094 acts as a conducting medium that carriesenergy from the ablation electrode 2092 to tissue of the patient as thesaline exits the distal tip 2022. In addition, the continuous flow ofthe saline acts to cool the ablation electrode 2092 in order to avoidsteaming at the ablation electrode/saline interface.

In some implementations, to further cool the ablation electrode 2092,the ablation electrode 2092 can be configured such that its outersurface is flush with the outer surface of the catheter shaft. The outersurface can also be coated with a thin insulator, such as parylene. Thisallows additional cooling of the metal though the blood. In certainimplementations, the electrode is made from one or more materials, suchas platinum iridium or gold, that provide additional cooling benefits tothe ablation electrode.

In some implementations, the ablation electrode can be situated on theouter rather than the inner surface of the conformable distal tip whichincludes shape activated valves. With this implementation, energy willnot be selectively applied using saline, however, selective coolingusing the shape activated valves can still be accomplished. Many of theother benefits, as described elsewhere, including the conforming of thetip to tissue and of the sensing components can still be accomplished.

In some implementations holes or slits not having valve action can beimplemented. With this implementation energy and saline will not beselectively applied. Many of the other benefits, as described elsewhere,including the conforming of the tip to tissue with its beneficial impacton lesion characteristics and of the sensing components can still beaccomplished.

While the neck 130 of the distal tip 122 has been described as beingattached to the catheter shaft 128 using a compression fit and/or amechanical connection, any of various other attachment techniques canalternatively or additionally be used to attach the distal tip 122 andthe various other distal tips described herein to the catheter shaft. Incertain implementations, for example, an electrically conductiveadhesive is disposed between the outer surface of the catheter shaft andthe inner surface of the neck to secure those components together. Theelectrically conductive adhesive, in addition to providing a securingfunction, can facilitate transmission of electrical energy from theconductive ring at the distal end of the catheter shaft to the ablationelectrode applied to the inner surface of the neck. Examples ofelectrically conductive adhesives that can be used include silver-filledsilicone RTV adhesive, Loctite 3888, for example.

While many of the distal tips discussed above have been described asincluding thermistors, other types of temperature sensors, such asthermocouples, can alternatively or additionally be used. For example,ink-based thermocouples can be applied directly to the outer surface ofthe tip. Alternatively, or additionally, ink based thermistors,thin-film elements (e.g., ink-on-flex circuits assembled on the tip),and other temperature sensors can be used.

While the distal tips discussed above have been described as having aspherical shape, distal tips of other shapes can be used. The shape ofthe distal tip can, for example, be selected to correspond to the shapeof an anatomical feature to be treated or to perform a particular typeof procedure desired. FIGS. 35 and 36 illustrate distal tips 2122, 2222that have tear drop and garlic clove shapes, respectively. The distalsection of the body of each of these tips is generally rounded orhemispherical and the proximal section tapers to a smaller diametertoward the proximal end. Such a distal tip shape can provide morestructural support in the proximal section while maintaining a largesurface area in the distal section, which allows for the formation oflarge lesions. In certain implementations, as shown in FIG. 37 , adistal tip 2322 having a football shape or hammerhead shark shape can beused. This type of tip can be particularly beneficial when ablationalong a line of contact with tissue is desired. FIG. 38 illustrates anopposed-cones shaped distal tip 2422, which can be used to make a lesionin the form of a circle when the conformable tip is pressed into anopening (e.g. of a vein) of arbitrary diameter. Any of various otherasymmetric shapes can alternatively be implemented in order toselectively ablate in one area, or to fit the distal tip into aparticularly shaped anatomical structure.

While the distal tip has generally been described as being loaded with aradiopaque additive such as a barium sulfate or bismuth additive, othermaterials and/or inks could be used to permit the distal tip to bevisualized using fluoroscopy, during an ablation treatment. In someimplementations, a stiffening material, e.g., Nitinol, can be added tothe distal tip to facilitate visualization during an ablation treatment.

The distal section of the catheter shaft 128 can be implemented assingle lumen. In other implementations, the catheter shaft includes twoor more lumens. In certain implementations, for example, the cathetershaft includes multiple lumens for separately housing the various wiresand cables and tube transporting the fluid.

While the ablation catheter 104 has been described as a bi-directional,steerable catheter, the catheter can alternatively be a unidirectional,steerable catheter. For example, rather than having two wires that arecircumferentially spaced by about 180 degrees and are attached to thering positioned at the distal end of the catheter shaft, a single wirecan extend along the catheter shaft and be attached to the ring. Inaddition, while the catheter has been described as including adeflectable or steerable catheter shaft, non-steerable catheter shaftscan alternatively be used in combination with or independently from afixed-curve or articulating sheath, or robotic navigation systems

While the ablation catheter 104 has been described as including aninsertion sheath that is retractable for constraining the distal tip 122in a collapsed configuration, other types of sheaths can be used. Insome implementations, for example, the sheath designed to be torn awayfrom the catheter shaft 128 after insertion of the distal tip 122 intothe patient. In this example, the torn sheath can be removed from thecatheter shaft 128.

While the tips of many ablation catheters described herein have beendescribed as expanding to a larger size after delivery into the patient,in some implementations a tip of an ablation catheter can expand to alarger size after being delivered to the treatment site.

While the ablation catheters above have been described as including asheath to constrain the distal tip in a collapsed configuration whilethe ablation catheter is being inserted through an introducer sheathinto the patient, other types of devices can alternatively oradditionally be used to constrain the distal tip 122 in its collapsedconfiguration. In some implementations, for example, the ablationcatheter includes an axially displaceable rod positioned within a lumenof the catheter shaft. The distal end of the rod typically terminates inor near the distal tip 122. In certain implementations, the distal endof the rod is attached to (e.g., mechanically attached to or adhesivelybonded to) the inner surface of the distal end of the distal tip. Thedistal end of the rod can include a bulbous head or some other type ofblunt feature to help prevent damage to the distal tip due to contactbetween the distal end of the rod and the inner surface of the distaltip. The proximal end of the rod extends proximally from the proximalend of the handle such that the user is able to grasp and manipulate theportion of the rod proximal to the handle. Prior to insertion of theablation catheter into the patient, the user can push the rod in thedistal direction. When doing so, the distal end of the rod contacts theinner surface of the distal end of the distal tip, causing the distaltip to lengthen and partially collapse. This technique reduces theoverall diameter of the distal tip, allowing it to be more easilyinserted into the patient. The rod can also incorporate the ablationelectrode in certain implementations.

While measured or monitored values have generally been described asimpedance values, other values, or parameters can be used. For example,voltage values and current values, and so forth can be additionally oralternatively be measured or monitored.

While data collected form the various sensors (e.g., electrodes,thermistors, etc.) has been described as being sent to the catheterinterface unit 108 for processing, the data can alternatively be sent toother devices for processing. In certain implementations, for example,data is sent from sensors of the ablation catheter to the mapping system112 and/or recording system 111.

While the catheter interface unit 108, the recording system 111, themapping system 112, the irrigation pump 114, and the ablation generator116 have been described as separate components, in certainimplementations, two or more of those components are integrated into asingle machine. In some implementations, for example, the catheterinterface unit is integrated with the ablation generator and theirrigation pump. In certain implementations, all of these components areintegrated into a single machine.

While the catheter interface unit 108 has been largely described asincluding a current source for generating a current signal (e.g., asinusoidal current signal at a particular frequency), the catheterinterface unit 108 can alternatively or additionally include a voltagesource for generating voltage waveforms. In some implementations, thecatheter interface unit 108 is configured to generate a sinusoidal orsquare wave voltage that is applied across the various electrodes, andthe resultant current running through the electrodes can be measured. Insome implementations, a combination of voltage and current measurementscan be used to determine impedances between electrodes.

While the systems above have been described as comparing impedancevalues (e.g., impedance between any combination of electrodes orelectrode components, including the external electrodes 146, theinternal electrodes 148, the ablation electrode 120, the returnelectrode 118, the central conductive component 150 of the externalelectrodes 146, the annular conductive component 152 of the externalelectrodes 146, etc.) to threshold values in order to makedeterminations (e.g., determinations related to contact between tissueand electrode(s), determinations related to valve state(s), etc.), otherimplementations are possible. For example, in some implementations,impedance values (or, e.g., combinations of impedance values) betweenthe central conductive component 150 of external electrodes 146 and theannular conductive component 152 of external electrodes 146 can be usedto determine a degree of contact between the tissue and the externalelectrodes 146 (e.g., rather than or in addition to simply making abinary determination of whether external electrodes 146 are in contactwith the tissue).

In some implementations, particular impedance values (or, e.g.,combinations of particular impedance values between various electrodes)can correspond to open/closed states of various values. The open/closedstates of various values can be mapped to an impedance profile of theelectrodes. In some implementations, impedance values between variouselectrodes can be measured, and the open/closed states of various valvescan be determined based on this cumulative impedance information (e.g.,rather than based on comparisons between the impedance values andcorresponding thresholds). In some implementations, impedance values canbe used to determine a degree of closure of various valves (e.g., ratherthan or in addition to simply making a binary determination of whethervalues are open or closed).

While the systems above have been described as using saline to carry theenergy from the ablation electrode to the patient's tissue, any ofvarious other biocompatible electrically conductive fluids canalternatively or additionally be used. In some examples, the saline is ahypertonic saline allowing improved energy delivery, e.g., through lowerimpedance.

In addition, while many of the ablation catheters described above relyon electrically conductive fluids to carry the RF energy from theablation electrode to the tissue, in some implementations, the ablationcatheter is configured to transmit RF energy directly from the ablationcatheter to the tissue of the patient. In some such implementations, forexample, the ablation electrode extends along the distal tip of theablation catheter and directly contacts the tissue to be ablated.Alternatively, or additionally, the energy can be conducted from theablation electrode to the tissue of the patient via electricallyconductive bodily fluids of the patient.

While the systems and methods described above relate to RF ablation, incertain implementations, other types of energy can be used with thesesystems and methods. For example, irreversible electroporation includesa sequence of brief but high voltage energy application to induce tissueapoptosis and form a lesion. One of the challenges associated withirreversible electroporation includes energy loss during energy deliveryto a target tissue. Energy loss is particularly problematic inendocardial applications where most of the energy is shunted away fromtissue towards blood due to blood's higher conductivity. Just as with RFablation, the systems and methods described herein are also particularlywell suited for irreversible electroporation because, for example, theconformal tip, shape activated valves, relatively large cathetertip-tissue contact area, and ability to know catheter state prior toenergy application allow selective application of the electroporationenergy to target tissue.

While the ablation catheter 104 has been described as being used toperform a cardiac ablation treatment, the ablation catheter 104 canalternatively or additionally be used to carry out various other typesof treatments. These other treatments include, but are not limited to:the ablation of tumors, the ablation of uterine tissue to controlexcessive uterine bleeding, renal and carotid denervation, and selectivedrug and biological agent delivery.

The systems, methods, and techniques described herein can beimplemented, at least in part, on a computing device and/or a mobilecomputing device. For example, the catheter interface unit 108 (FIG. 1 )can be implemented as a computing device and/or a mobile computingdevice. In some implementations, the mobile computing device can beconfigured to display information related to the ablation procedure.

The computing device can represent various forms of digital computers,such as laptops, desktops, workstations, personal digital assistants,servers, blade servers, mainframes, and other appropriate computers. Themobile computing device can represent various forms of mobile devices,such as personal digital assistants, cellular telephones, smartphones,and other similar computing devices. The components described herein,their connections and relationships, and their functions, are meant tobe examples only, and are not meant to be limiting.

The computing device can include a processor, a memory, and a storagedevice. The processor can process instructions for execution within thecomputing device, including instructions stored in the memory or on thestorage device to display graphical information for a GUI on an externalinput/output device, such as a display. In some implementations,multiple processors can be used, as appropriate, along with multiplememories and types of memory. Also, multiple computing devices can beconnected, with each device providing portions of the necessaryoperations (e.g., as a server bank, a group of blade servers, or amulti-processor system).

The memory can store information within the computing device. In someimplementations, the memory is a volatile memory unit or units. In someimplementations, the memory is a non-volatile memory unit or units. Thememory can also be another form of computer-readable medium, such as amagnetic or optical disk.

The storage device is capable of providing mass storage for thecomputing device. In some implementations, the storage device can be orcontain a computer-readable medium, such as a floppy disk device, a harddisk device, an optical disk device, or a tape device, a flash memory orother similar solid state memory device, or an array of devices,including devices in a storage area network or other configurations.Instructions can be stored in an information carrier. The instructions,when executed by one or more processing devices (for example, theprocessor), can perform one or more methods, such as those describedabove. The instructions can also be stored by one or more storagedevices such as computer- or machine-readable mediums (for example, thememory, the storage device, or memory on the processor). In someimplementations, the memory can store information received by themapping system 112, the recording system 111, the irrigation pump 114,and/or the ablation generator 116 described above with reference to FIG.1 .

In some implementations, the computing device can include expansionports, which can include various communication ports (e.g., USB,Bluetooth, Ethernet, wireless Ethernet) that can be coupled to one ormore input/output devices, such as a keyboard, a pointing device, ascanner, or a networking device such as a switch or router, e.g.,through a network adapter.

The computing device can be implemented in a number of different forms.For example, the computing device can be implemented as a standardserver, or multiple times in a group of such servers. In addition, thecomputing device can be implemented in a personal computer such as alaptop computer. The computing device can also be implemented as part ofa rack server system. Alternatively, components from the computingdevice can be combined with other components in a mobile device, such asa mobile computing device. Each of such devices can contain one or moreof the computing device and the mobile computing device, and an entiresystem can be made up of multiple computing devices communicating witheach other.

The mobile computing device can include a processor, a memory, aninput/output device such as a display, a communication interface, and atransceiver, among other components. The mobile computing device canalso be provided with a storage device, such as a micro-drive or otherdevice, to provide additional storage.

The processor can execute instructions within the mobile computingdevice, including instructions stored in the memory. The processor canbe implemented as a chipset of chips that include separate and multipleanalog and digital processors. The processor can provide, for example,for coordination of the other components of the mobile computing device,such as control of user interfaces, applications run by the mobilecomputing device, and wireless communication by the mobile computingdevice.

The processor can communicate with a user through a control interfaceand a display interface coupled to the display. The control interfacecan receive commands from a user and convert them for submission to theprocessor. In addition, an external interface can provide communicationwith the processor, so as to enable near area communication of themobile computing device with other devices. The external interface canprovide, for example, for wired communication in some implementations,or for wireless communication in other implementations, and multipleinterfaces can also be used.

The mobile computing device can be configured to display informationrelated to the ablation procedure. For example, the mobile computingdevice can be configured to present a digital readout of the actualpower, voltage and current being delivered, the calculated impedance(e.g., based on measured current and voltage) between electrodes (e.g.,between the ablation electrode 120 and the return electrode 118) duringthe delivery of energy, the measured temperature detected by the varioussensors, the number of times the ablation generator 116 has beenactivated, and/or the total elapsed time during which energy has beendelivered to the patient. In some implementations, the mobile computingdevice can display data that represents the shape of the distal tip 122or the shape and/or progress of the lesion being generated by theablation catheter 104. In some implementations, the mobile computingdevice can display the screenshots described above with reference toFIGS. 9 and 10 or similar screen shots.

The memory can store information within the mobile computing device. Thememory can be implemented as one or more of a computer-readable mediumor media, a volatile memory unit or units, or a non-volatile memory unitor units. An expansion memory can also be provided and connected to themobile computing device through an expansion interface, which caninclude, for example, a SIMM (Single In Line Memory Module) cardinterface. The expansion memory can provide extra storage space for themobile computing device, or can also store applications or otherinformation for the mobile computing device. Specifically, the expansionmemory can include instructions to carry out or supplement the processesdescribed above.

In some implementations, instructions are stored in an informationcarrier. The instructions, when executed by one or more processingdevices (for example, the processor), can perform one or more methods,such as those described above. The instructions can also be stored byone or more storage devices, such as one or more computer ormachine-readable mediums (for example, the memory, the expansion memory,or memory on the processor). In some implementations, the instructionscan be received in a propagated signal, for example, over thetransceiver or the external interface.

The mobile computing device can communicate wirelessly through thecommunication interface, which can include digital signal processingcircuitry where necessary. The communication interface can provide forcommunications under various modes or protocols understood to thoseskilled in the art. Such communication can occur, for example, throughthe transceiver using a radio-frequency. In addition, short-rangecommunication can occur, such as using a Bluetooth, WiFi, or other suchtransceiver. In addition, a GPS (Global Positioning System) receivermodule can provide additional navigation- and location-related wirelessdata to the mobile computing device, which can be used as appropriate byapplications running on the mobile computing device.

The mobile computing device can also communicate audibly using an audiocodec, which can receive spoken information from a user and convert itto usable digital information. The audio codec can likewise generateaudible sound for a user, such as through a speaker, e.g., in a handsetof the mobile computing device.

The mobile computing device can be implemented in a number of differentforms. For example, the mobile computing device can be implemented as acellular telephone. The mobile computing device can also be implementedas part of a smart-phone, a tablet, a personal digital assistant, orother similar mobile device.

Various implementations of the systems and techniques described here canbe realized in digital electronic circuitry, integrated circuitry,specially designed ASICs (application specific integrated circuits),computer hardware, firmware, software, and/or combinations thereof.These various implementations can include implementations in one or morecomputer programs that are executable and/or interpretable on aprogrammable system including at least one programmable processor, whichcan be special or general purpose, coupled to receive data andinstructions from, and to transmit data and instructions to, a storagesystem, at least one input device, and at least one output device.

These computer programs (also known as programs, software, softwareapplications or code) can include machine instructions for aprogrammable processor, and can be implemented in a high-levelprocedural and/or object-oriented programming language, and/or inassembly/machine language. As used herein, the terms machine-readablemedium and computer-readable medium refer to any computer programproduct, apparatus and/or device (e.g., magnetic discs, optical disks,memory, Programmable Logic Devices (PLDs)) used to provide machineinstructions and/or data to a programmable processor, including amachine-readable medium that receives machine instructions as amachine-readable signal. The term machine-readable signal refers to anysignal used to provide machine instructions and/or data to aprogrammable processor.

To provide for interaction with a user, the systems and techniquesdescribed here can be implemented on a computer having a display devicefor displaying information to the user and a keyboard and a pointingdevice by which the user can provide input to the computer. Other kindsof devices can be used to provide for interaction with a user as well.

The systems and techniques described here can be implemented in acomputing system that includes a back end component (e.g., as a dataserver), or that includes a middleware component (e.g., an applicationserver), or that includes a front end component (e.g., a client computerhaving a graphical user interface or a Web browser through which a usercan interact with an implementation of the systems and techniquesdescribed here), or any combination of such back end, middleware, orfront end components. The components of the system can be interconnectedby any form or medium of digital data communication (e.g., acommunication network). Examples of communication networks include alocal area network (LAN), a wide area network (WAN), and the Internet.

The computing system can include clients and servers. A client andserver are generally remote from each other and typically interactthrough a communication network. The relationship of client and serverarises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other.

C. Additional Examples

Several aspects of the present technology are set forth in the followingexamples.

1. An ablation catheter comprising:

-   -   a catheter body defining a fluid delivery lumen, and    -   a deformable tip secured to the catheter body,    -   wherein the ablation catheter is configured to permit liquid        communication between an interior of the deformable tip and an        exterior of the deformable tip in response to a deformation of        the tip.

2. The catheter of example 1 wherein the deformable tip is formed of anelastomeric material.

3. The catheter of example 1 or example 2 further comprising aconductive member configured to deliver current to liquid within thedeformable tip such that liquid passing from the interior of thedeformable tip to the exterior of the deformable tip can convey RFenergy away from the deformable tip.

4. The catheter of example 1, 2, or 3 wherein the ablation catheter isconfigured to emit RF energy away from the deformable tip in response tothe deformation of the deformable tip.

5. The catheter of example 4 wherein the RF energy is transmitted fromthe interior of the deformable tip to the exterior of the deformable tipvia liquid exiting the deformable tip.

6. The catheter of example 1, 2, 3, 4, or 5 wherein the deformable tipcomprises one or more valves, and wherein the one or more valves areconfigured to open in response to the deformation of the deformable tip.

7. The catheter of example 6 wherein the one or more valves comprise oneor more slits extending through a wall of the deformable tip.

8. The catheter of example 6 or example 7 wherein the one or more valvescomprise 3-legged slits extending through the wall of the deformabletip.

9. The catheter of example 7 or example 8 wherein the one or more slitsextend through a recessed region of the wall of the deformable tip.

10. The catheter of example 9 wherein the recessed region of the wall ofthe deformable tip is tetrahedral-shaped.

11. The catheter of example 9 wherein the recessed region of the wall ofthe deformable tip is hemispherical.

12. The catheter of example 6, 7, 8, 9, or 10 wherein the deformable tipcomprises support regions between adjacent valves.

13. The catheter of example 12 wherein the support regions compriseribs.

14. The catheter of example 13 wherein the ribs are attached at oppositeends to walls of adjacent valves.

15. The catheter of example 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,or 14 wherein a support structure is configured to support a proximalend region of the deformable tip.

16. The catheter of example 15 wherein the support structure includesone or more ribs that extend along the proximal end region of thedeformable tip.

17. The catheter of example 15 or example 16 wherein the supportstructure is integral with a wall of the deformable tip.

18. The catheter of example 15 or example 16 wherein the supportstructure is a component that is attached to the deformable tip.

19. The catheter of example 15, 16, 17, or 18 wherein the supportstructure comprises a plurality of fingers that extend along theproximal end region of the deformable tip.

The catheter of example 19 further comprising one or more electrodesattached to one or more of the fingers.

21. The catheter of example 20 wherein the fingers are flexible printedcircuits arranged to transmit signals to and from the one or moreelectrodes.

22. The catheter of example 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,14, 15, 16, 17, 18, 19, or 21 wherein the deformable tip has a thicknessof 0.20 mm or less.

23. The catheter of example 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,14, 15, 16, 17, 18, 19, 21, or 22 further comprising a conductivematerial along an inner surface of the deformable tip.

24. The catheter of example 23 wherein the conductive material isconductive to RF energy.

25. The catheter of example 23 or example 24 wherein the conductivematerial is a conductive layer.

26. The catheter of example 23, 24, or 25 wherein the conductive layercomprises conductive ink.

27. The catheter of example 23, 24, 25, or 26 wherein the conductivematerial extends along at least a portion of a neck of the deformabletip, and wherein the neck is secured to the catheter body such that theconductive material contacts a conductive element exposed along an outersurface of the catheter body.

28. The catheter of example 25, 26, or 27 wherein the conductive layercovers substantially an entire inner surface of the deformable tip.

29. The catheter of example 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,14, 15, 16, 17, 18, 19, 21, 22, 23, 24, 25, 26, 27, or 28 furthercomprising a conductive material along an inner surface of thedeformable tip.

30. The catheter of example 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,14, 15, 16, 17, 18, 19, 21, 22, 23, 24, 25, 26, 27, 28, or 29 wherein abody of the deformable tip comprises a conductive material.

31. The catheter of example 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,14, 15, 16, 17, 18, 19, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30further comprising an insulating layer along an outer surface of a/thebody of the deformable tip.

32. The catheter of example 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,14, 15, 16, 17, 18, 19, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, or 31wherein a/the body of the deformable tip comprises a polymeric materialcontaining conductive particles.

33. The catheter of example 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,14, 15, 16, 17, 18, 19, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, or32 wherein the ablation catheter is configured to cause liquid to flowfrom the interior of the deformable tip toward an object that is incontact with and deforming the deformable tip.

34. The catheter of example 33 wherein the object is tissue.

35. An ablation catheter comprising:

-   -   a catheter body;    -   a tip secured to the catheter body, wherein an inner surface of        the tip includes a conductive layer, and wherein the tip        comprises one or more valves configured to permit liquid        communication from an interior of the tip to an exterior of the        tip.

36. The ablation catheter of example 35 wherein the tip is deformable.

37. The catheter of example 36 wherein the deformable tip is formed ofan elastomeric material.

38. The catheter of example 35, 36, or 37 wherein the conductive layeris configured to deliver current to liquid within the tip such thatliquid passing from the interior of the tip to the exterior of the tipcan convey RF energy away from the tip.

39. The catheter of example 35, 36, 37, or 38 wherein the ablationcatheter is configured to emit RF energy away from the tip.

40. The catheter of example 39 wherein the RF energy is transmitted fromthe interior of the tip to the exterior of the tip via liquid exitingthe tip.

41. The catheter of example 35, 36, 37, 38, 39, or 40 wherein the one ormore valves are configured to open in response to deformation of thetip.

42. The catheter of example 35, 36, 378, 38, 39, 40, or 41 wherein theone or more valves comprise one or more slits extending through a wallof the tip.

43. The catheter of example 42 wherein the one or more slits extendthrough a recessed region of the wall of the tip.

44. The catheter of example 35, 36, 37, 38, 39, 40, 41, 42, or 43wherein the tip comprises support regions between adjacent valves.

45. The catheter of example 44 wherein the support regions compriseribs.

46. The catheter of example 45 wherein the ribs are attached at oppositeends to walls of adjacent valves.

47. The catheter of example 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45,or 46 wherein a support structure is configured to support a proximalend region of the tip.

48. The catheter of example 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45,46, or 47 wherein the tip has a thickness of 0.20 mm or less.

49. The catheter of example 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45,46, 47, or 48 wherein the conductive layer is conductive to RF energy.

50. The catheter of example 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45,46, 47, 48, or 49 wherein the conductive layer comprises conductive ink.

51. The catheter of example 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45,46, 47, 48, 49, or wherein the conductive layer extends along at least aportion of a neck of the tip, and wherein the neck is secured to thecatheter body such that the conductive layer contacts a conductiveelement exposed along an outer surface of the catheter body.

52. The catheter of example 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45,46, 47, 48, 49, 50, or 51 wherein the conductive layer coverssubstantially an entire inner surface of the tip.

53. The catheter of example 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45,46, 47, 48, 49, 50, 51, or 52 wherein the ablation catheter isconfigured to cause liquid to flow from the interior of the tip towardan object that is in contact with and deforming the tip.

54. An ablation catheter comprising:

-   -   a catheter body defining a fluid delivery lumen;    -   a deformable tip secured to the catheter body, the deformable        tip in fluid communication with the fluid delivery lumen; and    -   one or more deformable valves protruding from the deformable        tip,    -   wherein the one or more deformable valves define respective one        or more slits, and wherein each slit is openable in response to        deformation of the deformable tip.

55. The ablation catheter of example 54 wherein the one or moredeformable valves protrude radially outward from the deformable tip.

56. The ablation catheter of example 54 wherein the one or moredeformable valves protrude radially inward from the deformable tip.

57. The ablation catheter of example 54, 55, or 56 wherein the one ormore deformable valves are integral with the deformable tip.

58. The ablation catheter of example 54, 55, 56, or 57 wherein thedeformable tip is configured such that a fluid from the fluid deliverylumen flows through a slit in response to a deformation of a respectivedeformable valve of the one or more deformable valves.

59. The ablation catheter of example 54, 55, 56, 57, or 58 wherein thedeformable tip is configured such that fluid from the fluid deliverylumen exits the deformable tip through a slit in response to adeformation of a respective deformable valve of the one or moredeformable valves.

60. The ablation catheter of example 58 or example 59 wherein a flowrate of liquid exiting the deformable tip increases as a degree ofdeformation of the deformable tip increases.

61. The ablation catheter of example 54, 55, 56, 57, 58, 59, or 60wherein the deformable tip is formed of an elastomeric material.

62. The ablation catheter of example 54, 55, 56, 57, 58, 59, 60, or 61further comprising a conductive member configured to deliver current toliquid within the deformable tip such that liquid passing from aninterior of the deformable tip to an exterior of the deformable tip canconvey RF energy away from the deformable tip.

63. The ablation catheter of example 54, 55, 56, 57, 58, 59, 60, 61, or62 wherein the ablation catheter is configured to emit RF energy awayfrom the deformable tip in response to the deformation of the deformabletip.

64. The ablation catheter of example 63 wherein the RF energy istransmitted from an interior of the deformable tip to an exterior of thedeformable tip via liquid exiting the deformable tip.

65. The ablation catheter of example 54, 55, 56, 57, 58, 59, 60, 61, 62,63, or 64 wherein the deformable tip comprises support regions betweenadjacent valves.

66. The ablation catheter of example 65 wherein the support regionscomprise ribs.

67. The ablation catheter of example 66 wherein the ribs are attached atopposite ends to walls of adjacent valves.

68. The ablation catheter of example 54, 55, 56, 57, 58, 59, 60, 61, 62,63, 64, 65, 66, or 67 wherein a support structure is configured tosupport a proximal end region of the deformable tip.

69. The ablation catheter of example 54, 55, 56, 57, 58, 59, 60, 61, 62,63, 64, 65, 66, 67, or 68 wherein the deformable tip has a thickness of0.20 mm or less.

70. The ablation catheter of example 54, 55, 56, 57, 58, 59, 60, 61, 62,63, 64, 65, 66, 67, 68, or 69 further comprising a conductive materialalong an inner surface of the deformable tip.

71. The ablation catheter of example 70 wherein the conductive materialis conductive to RF energy.

72. The ablation catheter of example 70 or example 71 wherein theconductive material is a conductive layer.

73. The ablation catheter of example 72 wherein the conductive layercomprises conductive ink.

74. The ablation catheter of example 70, 71, 72, or 73 wherein theconductive material extends along at least a portion of a neck of thedeformable tip, and wherein the neck is secured to the catheter bodysuch that the conductive material contacts a conductive element exposedalong an outer surface of the catheter body.

75. The ablation catheter of example 70, 71, 72, 73, or 74 wherein theconductive material covers substantially an entire inner surface of thedeformable tip.

76. The ablation catheter of example 54, 55, 56, 57, 58, 59, 60, 61, 62,63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, or 75 wherein a body ofthe deformable tip comprises a conductive material.

77. The ablation catheter of example 54, 55, 56, 57, 58, 59, 60, 61, 62,63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, or 76 furthercomprising an insulating layer along an outer surface of a/the body ofthe deformable tip.

78. The ablation catheter of example 54, 55, 56, 57, 58, 59, 60, 61, 62,63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, or 77 whereina/the body of the deformable tip comprises a polymeric materialcontaining conductive particles.

79. The ablation catheter of example 54, 55, 56, 57, 58, 59, 60, 61, 62,63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, or 78wherein the ablation catheter is configured to cause liquid to flow froman interior of the deformable tip toward an object that is in contactwith and deforming the deformable tip.

80. An ablation catheter comprising:

-   -   a catheter body;    -   a deformable tip secured to the catheter body, wherein an end        region of the deformable tip comprises a support structure        configured to limit deformation of the end region in response to        a proximal or lateral force applied to the deformable tip.

81. The ablation catheter of example 80 wherein the end region of thedeformable tip is a proximal end region of the deformable tip.

82. The ablation catheter of example 80 or example 81 wherein the endregion of the deformable tip comprises a proximal surface of a body ofthe deformable tip.

83. The ablation catheter of example 80, 81, or 82 wherein the endregion of the deformable tip comprises a neck of the deformable tip.

84. The ablation catheter of example 80, 81, 82, or 83 wherein thesupport structure includes one or more ribs that extend along the endregion of the deformable tip.

85. The ablation catheter of example 80, 81, 82, 83, or 84 wherein thesupport structure is integral with a wall of the deformable tip.

86. The ablation catheter of example 80, 81, 82, 83, or 84 wherein thesupport structure is a component that is attached to the deformable tip.

87. The ablation catheter of example 80, 81, 82, 83, 84, 85, or 86wherein the support structure comprises a plurality of fingers thatextend along the end region of the deformable tip.

88. The ablation catheter of example 87 further comprising one or moreelectrodes attached to one or more fingers of the plurality of fingers.

89. The ablation catheter of example 88 wherein the one of more fingersare flexible printed circuits arranged to carry signals to and from theone or more electrodes.

90. The ablation catheter of example 88 or example 89 wherein the one ormore electrodes are flexible printed circuits.

91. The ablation catheter of example 87, 88, 89, or 90 furthercomprising a patterned layer of stiffening material on the plurality offingers, wherein the patterned layer comprises multiple discretesegments that increase in width as the multiple discrete segments extendaway from the plurality of fingers.

92. The ablation catheter of example 91 wherein the multiple discretesegments are wider along a top edge of the multiple discrete segmentsthan along a bottom edge of the multiple discrete segments.

93. The ablation catheter of example 91 or example 92 wherein themultiple discrete segments are configured to inhibit a radial inwardforce applied to the end region of the deformable tip from inwardlydeflecting the end region of the deformable tip.

94. The ablation catheter of example 80, 81, 82, 83, 84, 85, 86, 87, 88,89, 90, 91, 92, or 93 wherein the support structure comprises a stiffmember that is attached the catheter body and that extends into aninterior of the deformable tip, and wherein a plurality of tethers isanchored at one end to the stiff member and at another end to thedeformable tip.

95. The ablation catheter of example 80, 81, 82, 83, 84, 85, 86, 87, 88,89, 90, 91, 92, 93, or 94 wherein the deformable tip is formed of anelastomeric material.

96. The ablation catheter of example 80, 81, 82, 83, 84, 85, 86, 87, 88,89, 90, 91, 92, 93, 94, or 95 further comprising a conductive memberconfigured to deliver current to liquid within the deformable tip suchthat liquid passing from an interior of the deformable tip to anexterior of the deformable tip can convey RF energy away from thedeformable tip.

97. The ablation catheter of example 80, 81, 82, 83, 84, 85, 86, 87, 88,89, 90, 91, 92, 93, 94, 95, or 96 wherein the ablation catheter isconfigured to emit RF energy away from the deformable tip in response todeformation of the deformable tip.

98. The ablation catheter of example 96 or example 97 wherein the RFenergy is transmitted from an interior of the deformable tip to anexterior of the deformable tip via liquid exiting the deformable tip.

99. The ablation catheter of example 80, 81, 82, 83, 84, 85, 86, 87, 88,89, 90, 91, 92, 93, 94, 95, 96, 97, or 98 wherein the deformable tipcomprises one or more valves, and wherein the one or more valves areconfigured to open in response to deformation of the deformable tip.

100. The ablation catheter of example 99 wherein the one or more valvescomprise one or more slits extending through a wall of the deformabletip.

101. The ablation catheter of example 99 or example 100 wherein thedeformable tip comprises support regions between adjacent valves.

102. The ablation catheter of example 101 wherein the support regionscomprise ribs.

103. The ablation catheter of example 102 wherein the ribs are attachedat opposite ends to walls of the adjacent valves.

104. The ablation catheter of example 80, 81, 82, 83, 84, 85, 86, 87,88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, or 103wherein the deformable tip has a thickness of 0.20 mm or less.

105. The ablation catheter of example 80, 81, 82, 83, 84, 85, 86, 87,88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, or104 further comprising a conductive material on a surface of thedeformable tip.

106. The ablation catheter of example 105 wherein the conductivematerial is conductive to RF energy.

107. The ablation catheter of example 104 or example 105 wherein theconductive material is a conductive layer.

108. The ablation catheter of example 107 wherein the conductive layercomprises conductive ink.

109. The ablation catheter of example 107 or example 108 wherein theconductive layer covers substantially an entire inner surface of thedeformable tip.

110. The ablation catheter of example 80, 81, 82, 83, 84, 85, 86, 87,88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104,105, 106, 107, 108, or 109 wherein a body of the deformable tipcomprises a conductive material.

111. The ablation catheter of example 80, 81, 82, 83, 84, 85, 86, 87,88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104,105, 106, 107, 108, 109, or 110 further comprising an insulating layeralong a surface of a/the body of the deformable tip.

112. The ablation catheter of example 80, 81, 82, 83, 84, 85, 86, 87,88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104,105, 106, 107, 108, 109, 110, or 111 wherein a/the body of thedeformable tip comprises a polymeric material containing conductiveparticles.

113. The ablation catheter of example 80, 81, 82, 83, 84, 85, 86, 87,88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104,105, 106, 107, 108, 109, 110, 111, or 112 wherein the ablation catheteris configured to cause liquid to flow from an interior of the deformabletip toward an object that is in contact with and deforming thedeformable tip.

114. A method comprising:

-   -   viewing a deformable tip of an ablation catheter via        fluoroscopy; and    -   advancing the ablation catheter toward an object until a        deformation of the deformable tip is viewed.

115. The method of example 114 wherein advancing the ablation catheterincludes advancing the ablation catheter until a predetermined level ofdeformation of the deformable tip is viewed.

116. The method of example 115 wherein the predetermined level ofdeformation of the deformable tip is a deformation that displaces asurface of the deformable tip by ⅓ to ½ of an undeformed diameter of thedeformable tip.

117. The method of example 114, 115, or 116 further comprisingidentifying a contact region between the deformable tip and the objectbased on the viewing.

118. The method of example 117 wherein the contact region is graphicallydisplayed on a graphical user interface.

119. The method of example 117 or example 118 further comprisingincreasing an area of contact between the deformable tip and the objectby further advancing the ablation catheter.

120. The method of example 114, 115, 16, 117, 118, or 119 wherein thedeformation of the deformable tip causes one or more valves of thedeformable tip to open such that liquid emits from an interior of thedeformable tip to an exterior of the deformable tip.

121. The method of example 114, 115, 116, 117, 118, 119, or 120 furthercomprising collecting data from one or more sensors of the ablationcatheter.

122. The method of example 121 further comprising determining a shape ofthe deformable tip based on the collected data.

123. The method of example 122 wherein the shape of the deformable tipis graphically displayed on a graphical user interface.

124. The method of example 121, 122, or 123 wherein the one or moresensors are electrodes.

125. The method of example 121, 122, 123, or 124 further comprisingdetermining a temperature of the deformable tip based on the collecteddata.

126. The method of example 125 wherein the temperature of the deformabletip is graphically displayed on a graphical user interface.

127. The method of example 121, 122, 123, 124, 125, or 126 wherein theone or more sensors are temperature sensors.

128. The method of example 121, 122, 123, 124, 125, 126, or 127 whereinthe one or more sensors are secured to the deformable tip.

129. The method of example 114, 115, 116, 117, 118, 119, 120, 121, 122,123, 124, 125, 126, 127, or 128 wherein the object is tissue, andwherein the method further comprises ablating the tissue.

130. The method of example 129 wherein ablating the tissue comprisesdelivering RF energy to the tissue.

131. The method of example 130 wherein delivering RF energy to thetissue comprises delivering liquid from an interior of the deformabletip to an exterior of the deformable tip, the liquid serving as aconduit for the RF energy.

132. The method of example 131 wherein the liquid travels from theinterior of the deformable tip to the exterior of the deformable tip viavalves of the deformable tip that open when a portion of the deformabletip comprising the valves is deformed.

133. An ablation catheter comprising:

-   -   a catheter body including a fluid delivery lumen;    -   a deformable tip secured to the catheter body, the deformable        tip including a conductive material; and    -   one or more electrodes secured to an exterior surface of the        deformable tip.

134. The ablation catheter of example 133 wherein the one or moreelectrodes are secured directly to the exterior surface of thedeformable tip.

135. The ablation catheter of example 133 wherein the one or moreelectrodes are secured to a member that extends along the exteriorsurface of the deformable tip and that is secured to the exteriorsurface of the deformable tip.

136. The ablation catheter of example 133, 134, or 135 furthercomprising one or more temperature sensors in thermal communication withthe one or more electrodes, and wherein the one or more temperaturesensors are thermally insulated from the conductive material and/or fromfluid contained in the deformable tip.

137. The ablation catheter of example 136 wherein the one or moretemperature sensors thermally communicate with the one or moreelectrodes through a nonconductive material.

138. The ablation catheter of example 137 wherein the nonconductivematerial is a polyamide.

139. The ablation catheter of example 136, 137, or 138 wherein the oneor more temperature sensors are thermistors.

140. The ablation catheter of example 133, 134, 135, 136, 137, 138, or139 wherein the one or more electrodes comprise one or more pairs ofconcentric electrodes secured to the exterior surface of the deformabletip, and wherein each pair of concentric electrodes comprises a centralconductive member and an annular conductive member surrounding thecentral conductive member.

141. The ablation catheter of example 140 wherein the one or more pairsof concentric electrodes are configured to generate a bipolar signal.

142. The ablation catheter of example 140 or example 141 wherein the oneor more pairs of concentric electrodes are configured in a manner suchthat values resulting from current driven between the central conductivemember and the annular conductive member can be used to determinecontact between the deformable tip and tissue.

143. The ablation catheter of example 140, 141, or 142 wherein the oneor more pairs of concentric electrodes are configured in a manner suchthat values resulting from voltage driven between the central conductivemember and the annular conductive member can be used to determinecontact between the deformable tip and tissue.

144. The ablation catheter of example 133, 134, 135, 136, 137, 138, 139,140, 141, 142, or 143 wherein the ablation catheter is configured toheat liquid that passes through the fluid delivery lumen and into thedeformable tip.

145. The ablation catheter of example 133, 134, 135, 136, 137, 138, 139,140, 141, 142, 143, or 144 wherein the conductive material is a firstconductive material, and wherein the first conductive material issecured to an inner surface of a proximal end region of the deformabletip, and further wherein a second conductive material is secured to aninner surface of a distal end region of the deformable tip for heatingliquid in the deformable tip.

146. The ablation catheter of example 145 wherein the first conductivematerial and the second conductive material are electrodes.

147. The ablation catheter of example 146 further comprising one or morewires connected to the electrodes secured to the inner surface of thedeformable tip for delivering electrical energy from a generator to theelectrodes secured to the inner surface of the deformable tip.

148. The ablation catheter of example 133, 134, 135, 136, 137, 138, 139,140, 141, 142, 143, 144, 145, 146, or 147 comprising a heating elementpositioned along the fluid delivery lumen of the catheter body.

149. The ablation catheter of example 148 wherein the heating elementcomprises a tubular electrode positioned along the catheter body, andwherein the tubular electrode defines a portion of the fluid deliverylumen and is configured to heat liquid that passes through the fluiddelivery lumen.

150. The ablation catheter of example 133, 134, 135, 136, 137, 138, 139,140, 141, 142, 143, 144, 145, 146, 147, 148, or 149 comprising arod-shaped electrode that extends distally from a distal end of thecatheter body and into an interior of the deformable tip, and whereinthe rod-shaped electrode is configured to heat liquid that passesthrough the fluid delivery lumen and into the interior of the deformabletip.

151. The catheter of example 133, 134, 135, 136, 137, 138, 139, 140,141, 142, 143, 144, 145, 146, 147, 148, 149, or 150 wherein thedeformable tip is formed of an elastomeric material.

152. The catheter of example 133, 134, 135, 136, 137, 138, 139, 140,141, 142, 143, 144, 145, 146, 147, 148, 149, 150, or 151 wherein theconductive material is configured to deliver current to liquid withinthe deformable tip such that liquid passing from an interior of thedeformable tip to an exterior of the deformable tip can convey RF energyaway from the deformable tip.

153. The catheter of example 133, 134, 135, 136, 137, 138, 139, 140,141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, or 152 whereinthe ablation catheter is configured to emit RF energy away from thedeformable tip in response to deformation of the deformable tip.

154. The catheter of example 152 or example 153 wherein the RF energy istransmitted from an interior of the deformable tip to an exterior of thedeformable tip via liquid exiting the deformable tip.

155. The catheter of example 133, 134, 135, 136, 137, 138, 139, 140,141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, or 154wherein the deformable tip has a thickness of mm or less.

156. The catheter of example 133, 134, 135, 136, 137, 138, 139, 140,141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, or155 wherein the conductive material is positioned along a surface of thedeformable tip.

157. The catheter of example 133, 134, 135, 136, 137, 138, 139, 140,141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154,155, or 156 wherein the conductive material is conductive to RF energy.

158. The catheter of example 133, 134, 135, 136, 137, 138, 139, 140,141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154,155, 156, or 157 wherein the conductive material is a conductive layer.

159. The catheter of example 158 wherein the conductive layer comprisesconductive ink.

160. The catheter of example 158 or example 159 wherein the conductivelayer covers substantially an entire inner surface of the deformabletip.

161. The catheter of example 133, 134, 135, 136, 137, 138, 139, 140,141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154,155, 156, 157, 158, 159, or 160 wherein a body of the deformable tipcomprises the conductive material.

162. The catheter of example 133, 134, 135, 136, 137, 138, 139, 140,141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154,155, 156, 157, 158, 159, 160 or 161 further comprising an insulatinglayer along a surface of a/the body of the deformable tip.

163. The catheter of example 133, 134, 135, 136, 137, 138, 139, 140,141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154,155, 156, 157, 158, 159, 160, 161, or 162 wherein a/the body of thedeformable tip comprises a polymeric material containing conductiveparticles.

164. The catheter of example 133, 134, 135, 136, 137, 138, 139, 140,141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154,155, 156, 157, 158, 159, 160, 161, 162, or 163 wherein the ablationcatheter is configured to cause liquid to flow from an interior of thedeformable tip toward an object that is in contact with and deformingthe deformable tip.

165. A tissue ablation method, comprising:

-   -   delivering energy to tissue during a first phase, wherein an        energy generator used to generate the delivered energy is set to        a first power setting during the first phase;    -   delivering energy to the tissue during a second phase, wherein        the energy generator used to generate the delivered energy is        set to a second power setting during the second phase, and        wherein the second power setting is different than the first        power setting such that a penetration depth of the delivered        energy into the tissue during the second phase differs from a        penetration depth of the delivered energy into the tissue during        the first phase.

166. The tissue ablation method of example 165 wherein the second powersetting is higher than the first power setting such that the penetrationdepth of the delivered energy into the tissue during the second phase isgreater than the penetration depth of the delivered energy into thetissue during the first phase.

167. The tissue ablation method of example 165 or example 166 furthercomprising delivering a cooling fluid to the tissue at a first flow rateduring the first phase.

168. The tissue ablation method of example 167 further comprisingdelivering the cooling fluid to the tissue at a second flow rate duringthe second phase, wherein the second flow rate is different than fromthe first flow rate.

169. The tissue ablation method of example 165, 166, 167, or 168 furthercomprising delivering energy to the tissue during a third phase, whereinthe energy generator used to generate the delivered energy is set to athird power setting during the third phase, and wherein the third powersetting is different than the first and the second power settings.

170. The tissue ablation method of example 169 further comprisingdelivering the cooling fluid to the tissue at a third flow rate duringthe third phase, wherein the third flow rate is different than the firstand the second flow rates.

171. The tissue ablation method of example 170 wherein the third flowrate is lower than the first and the second flow rates.

172. The method of example 165, 166, 167, 168, 169, 170, or 171 whereinthe energy delivered to the tissue ablates the tissue.

173. The method of example 165, 166, 167, 168, 169, 170, 171, or 172wherein the energy delivered to the tissue is RF energy.

174. The method of example 173 wherein the RF energy is delivered to thetissue by delivering liquid from an interior of a deformable tip of anablation catheter to an exterior of the deformable tip of the ablationcatheter, the liquid serving as a conduit for the RF energy.

175. The method of example 174 wherein the liquid travels from theinterior of the deformable tip to the exterior of the deformable tip viavalves of the deformable tip that open when a portion of the deformabletip comprising the valves is deformed.

176. The method of example 165, 166, 167, 168, 169, 170, 171, 172, 173,or 174 further comprising collecting data from one or more sensors ofthe ablation catheter.

177. The method of example 176 further comprising determining a shape ofthe deformable tip based on the collected data.

178. The method of example 177 further comprising graphically displayingthe shape of the deformable tip on a graphical user interface.

179. The method of example 176, 177, or 178 further comprisingdetermining a contact region between the deformable tip and the tissuebased on the collected data.

180. The method of example 179 further comprising graphically displayingthe contact region on a graphical user interface.

181. The method of example 176, 177, 178, 179, or 180 wherein the one ormore sensors are electrodes.

182. The method of example 176, 177, 178, 179, 180, or 181 furthercomprising determining a temperature of the deformable tip based on thecollected data.

183. The method of example 182 further comprising graphically displayingthe temperature of the deformable tip on a graphical user interface.

184. The method of example 176, 177, 178, 179, 180, 181, 182, or 183wherein the one or more sensors are temperature sensors.

185. The method of example 176, 177, 178, 179, 180, 181, 182, 183, or184 wherein the one or more sensors are secured to the deformable tip.

186. An ablation catheter comprising:

-   -   a catheter body;    -   a deformable tip secured to the catheter body,    -   wherein the ablation catheter is configured to emit RF energy in        a direction 330° or less about the deformable tip.

187. An ablation catheter comprising:

-   -   a catheter body;    -   a deformable tip secured to the catheter body wherein, the        deformable tip includes one or more valves, and wherein the        deformable tip is configured such that valves in no more than 90        percent of a surface area of the deformable tip open when the        deformable tip is deformed by tissue.

188. An ablation catheter comprising:

-   -   a catheter body;    -   a deformable tip secured to the catheter body, wherein the        deformable tip comprises one or more valves, and wherein the        deformable tip comprises at least one support region associated        with each of the one or more valves.

189. The catheter of example 188 wherein the support regions are locatedbetween adjacent valves.

190. The catheter of example 188 or example 189 wherein the supportregions comprise ribs.

191. The catheter of example 190 wherein the ribs are attached atopposite ends to walls of adjacent valves.

192. A method comprising:

-   -   measuring a first value or set of values resulting from an        electrical current driven between two or more electrodes secured        to a deformable tip of a catheter,    -   measuring a second value or set of values resulting from an        electrical current driven between the two or more electrodes        secured to the deformable tip of the catheter, and    -   determining a state of one or more valves of the deformable tip        based on a comparison between the first and second values or the        first and second sets of values.

193. The method of example 192 wherein determining the state of the oneor more valves comprises determining whether the one or more valves areopen or closed.

194. The method of example 192 or example 193 wherein determining thestate of the one or more valves comprises determining the state of atleast one valve in a first region of the deformable tip and determiningthe state of at least one valve in a second region of the deformabletip.

195. The method of example 194 wherein determining the state of thevalves in the first and second regions of the deformable tip comprisesdetermining whether the valves in the first and second regions of thedeformable tip are open or closed.

196. The method of example 192, 193, 194, or 195 wherein at least one ofthe two or more electrodes is within the deformable tip.

197. The method of example 192, 193, 194, 195, or 196 wherein at leastone of the two or more electrodes is outside of the deformable tip.

198. The method of example 192, 193, 194, 195, 196, or 197 wherein theelectrical current is driven between at least one electrode within thedeformable tip and an electrode outside of the deformable tip.

199. The method of example 192, 193, 194, 195, 196, 197, or 198 whereina location of an opened valve in the one or more valves corresponds to ageometrical configuration of the deformable tip.

200. The method of example 199 further comprising generating a visualrepresentation of the geometrical configuration of the deformable tip.

201. The method of example 192, 193, 194, 195, 196, 197, 198, 199, or200 wherein at least one of the two or more electrodes is a concentricelectrode that includes a central conductive member and an annularconductive member surrounding the central conductive member.

202. The method of example 192, 193, 194, 195, 196, 197, 198, 199, 200,or 201 further comprising generating a visual representation of alocation of an opened valve in one or more valves.

203. The method of example 192, 193, 194, 195, 196, 197, 198, 199, 200,201, or 202 wherein the first value or set of values is associated withthe deformable tip in a known state, and wherein the second value or setof values is associated with the deformable tip in an unknown state.

204. The method of example 203 wherein the known state is a state inwhich all valves of the deformable tip are closed.

D. Conclusion

The above detailed descriptions of implementations of the technology arenot intended to be exhaustive or to limit the technology to the preciseform disclosed above. Although specific implementations of, and examplesfor, the technology are described above for illustrative purposes,various equivalent modifications are possible within the scope of thetechnology, as those skilled in the relevant art will recognize. Forexample, while steps are presented in a given order, alternativeimplementations can perform steps in a different order. Furthermore, thevarious implementations described herein can also be combined to providefurther implementations.

From the foregoing, it will be appreciated that specific implementationsof the technology have been described herein for purposes ofillustration, but well-known structures and functions have not beenshown or described in detail to avoid unnecessarily obscuring thedescription of the implementations of the technology. Where the contextpermits, singular or plural terms can also include the plural orsingular term, respectively. Moreover, unless the word “or” is expresslylimited to mean only a single item exclusive from the other items inreference to a list of two or more items, then the use of “or” in such alist is to be interpreted as including (a) any single item in the list,(b) all of the items in the list, or (c) any combination of the items inthe list. Where the context permits, singular or plural terms can alsoinclude the plural or singular term, respectively. Additionally, theterms “comprising,” “including,” “having” and “with” are used throughoutto mean including at least the recited feature(s) such that any greaternumber of the same feature and/or additional types of other features arenot precluded. To the extent any materials incorporated herein byreference conflict with the present disclosure, the present disclosurecontrols.

From the foregoing, it will also be appreciated that variousmodifications can be made without deviating from the technology. Forexample, various components of the technology can be further dividedinto subcomponents, or that various components and functions of thetechnology can be combined and/or integrated. Furthermore, althoughadvantages associated with certain implementations of the technologyhave been described in the context of those implementations, otherimplementations can also exhibit such advantages, and not allimplementations need necessarily exhibit such advantages to fall withinthe scope of the technology.

1. An ablation catheter comprising: a catheter body; a tip secured tothe catheter body, wherein an inner surface of the tip includes aconductive layer, wherein the tip comprises one or more valvesconfigured to permit liquid communication from an interior of the tip toan exterior of the tip, and wherein the conductive layer is configuredto deliver current to liquid within the tip such that liquid passingfrom the interior of the tip to the exterior of the tip can convey RFenergy away from the tip.
 2. The ablation catheter of claim 1, whereinthe tip is deformable.
 3. The catheter of claim 2, wherein thedeformable tip is formed of an elastomeric material.
 4. The catheter ofclaim 1, wherein the ablation catheter is configured to emit RF energyaway from the tip.
 5. The catheter of claim 4, wherein the RF energy istransmitted from the interior of the tip to the exterior of the tip vialiquid exiting the tip.
 6. The catheter of claim 1, wherein the one ormore valves are configured to open in response to deformation of thetip.
 7. The catheter of claim 6, wherein the one or more valves compriseone or more slits extending through a wall of the tip.
 8. The catheterof claim 7, wherein the one or more slits extend through a recessedregion of the wall of the tip.
 9. The catheter of claim 1, wherein thetip comprises support regions between adjacent valves.
 10. The catheterof claim 9, wherein the support regions comprise ribs.
 11. The catheterof claim 10, wherein the ribs are attached at opposite ends to walls ofadjacent valves.
 12. The catheter of claim 1, wherein a supportstructure is configured to support a proximal end region of the tip. 13.The catheter of claim 1, wherein the tip has a thickness of 0.20 mm orless.
 14. The catheter of claim 1, wherein the conductive layer isconductive to RF energy.
 15. The catheter of claim 4, wherein theconductive layer comprises conductive ink.
 16. The catheter of claim 1,wherein the conductive layer extends along at least a portion of a neckof the tip, and wherein the neck is secured to the catheter body suchthat the conductive layer contacts a conductive element exposed along anouter surface of the catheter body.
 17. The catheter of claim 1, whereinthe conductive layer covers substantially an entire inner surface of thetip.
 18. The catheter of claim 1, wherein the ablation catheter isconfigured to cause liquid to flow from the interior of the tip towardan object that is in contact with and deforming the tip.
 19. An ablationcatheter comprising: a catheter body; a deformable tip secured to thecatheter body; and a conductive member configured to deliver current toliquid within the deformable tip such that liquid passing from theinterior of the deformable tip to the exterior of the deformable tip canconvey RF energy away from the deformable tip.
 20. The catheter of claim19, wherein the tip comprises one or more valves configured to permitliquid communication from an interior of the tip to an exterior of thetip.